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Glycogen Metabolism

Glycogen is a branched polymer and the storage form of carbohydrates Carbohydrates A class of organic compounds composed of carbon, hydrogen, and oxygen in a ratio of cn(H2O)n. The largest class of organic compounds, including starch; glycogen; cellulose; polysaccharides; and simple monosaccharides. Basics of Carbohydrates in the human body. Major sites of storage are the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy and skeletal muscles Skeletal muscles A subtype of striated muscle, attached by tendons to the skeleton. Skeletal muscles are innervated and their movement can be consciously controlled. They are also called voluntary muscles. Muscle Tissue: Histology. Glycogen is the main source of energy during fasting or in between meals. Glycogen provides energy for up to 18 hours, after which energy requirements are met MET Preoperative Care by fatty acid oxidation. The 2 metabolic pathways of glycogen are glycogenesis (glycogen synthesis Synthesis Polymerase Chain Reaction (PCR)) and glycogenolysis (glycogen breakdown). The key regulatory enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body's constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes in these processes are glycogen synthase (in glycogenesis) and glycogen phosphorylase (in glycogenolysis). These pathways proceed depending on the energy needs of the cells, generally modulated by hormonal and allosteric regulators. Abnormal accumulation of glycogen occurs with enzyme deficiencies causing different types of glycogen storage disorders Glycogen storage disorders Glycogen storage disorders (GSDs) are genetic defects leading to disorders of carbohydrate metabolism. The disorders are caused by pathogenic variants in genes that affect enzymes involved in glycogen breakdown. Deficiency of 1 of these enzymes may occur in the liver or muscles and can cause hypoglycemia and/or abnormal glycogen deposition in tissues. Glycogen Storage Disorders.

Last updated: Oct 18, 2022

Editorial responsibility: Stanley Oiseth, Lindsay Jones, Evelin Maza

Overview

Structure

  • Glycogen is an extensively branched polymer of alpha-d-glucose.
    • The animal analog to starch 
    • The straight chains are alpha-1,4 links, and the branched chains are alpha-1,6 links. 
  • Branching occurs every 8–10 units, making it more globular and less space consuming and allowing for increased solubility and quicker metabolization. 
Structure of glycogen

Structure of glycogen:
Glycogen consists of a core protein and is surrounded by 30,000–50,000 glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance units.

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Functions

  • The storage form of glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance, utilized when blood glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance (BG) level drops
  • Muscle glycogen:
    • Available for glycolysis Glycolysis Glycolysis is a central metabolic pathway responsible for the breakdown of glucose and plays a vital role in generating free energy for the cell and metabolites for further oxidative degradation. Glucose primarily becomes available in the blood as a result of glycogen breakdown or from its synthesis from noncarbohydrate precursors (gluconeogenesis) and is imported into cells by specific transport proteins. Glycolysis in the muscle; acts as a reserve fuel for the contraction of muscles
    • Skeletal muscle itself is unable to release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology glycogen into the bloodstream due to a lack of glucose-6-phosphatase Glucose-6-phosphatase An enzyme that catalyzes the conversion of d-glucose 6-phosphate and water to d-glucose and orthophosphate. Gluconeogenesis (G6Pase). 
  • Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy glycogen is responsible for maintaining BG levels, especially during fasting or exercise.

Storage

  • The major sites of storage of glycogen are skeletal muscle and the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy:
    • Hepatic glycogen content: 10 g/100 g tissue 
    • Skeletal muscle glycogen content: 1–2 g/100 g
  • The total quantity of muscle glycogen is more than liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy glycogen due to larger muscle mass Mass Three-dimensional lesion that occupies a space within the breast Imaging of the Breast.

Metabolic pathways

There are 2 main metabolic pathways of glycogen:

  1. Glycogenesis: synthesis Synthesis Polymerase Chain Reaction (PCR) of glycogen 
  2. Glycogenolysis: breakdown of glycogen

Glycogenesis

Definition

  • The synthesis Synthesis Polymerase Chain Reaction (PCR) of glycogen, storing excess glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance for future use
  • Process is not de novo and involves the addition of glycosyl residues to already-existing glycogen molecules. 

Step 1

Isomerization of glucose-6-phosphate Glucose-6-phosphate An ester of glucose with phosphoric acid, made in the course of glucose metabolism by mammalian and other cells. It is a normal constituent of resting muscle and probably is in constant equilibrium with fructose-6-phosphate. Gluconeogenesis to glucose-1-phosphate

  • Glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance addition to glycogen is initiated by the phosphorylation Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Post-translational Protein Processing of glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance to glucose-6-phosphate Glucose-6-phosphate An ester of glucose with phosphoric acid, made in the course of glucose metabolism by mammalian and other cells. It is a normal constituent of resting muscle and probably is in constant equilibrium with fructose-6-phosphate. Gluconeogenesis
    • Enzyme converting glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance to glucose-6-phosphate Glucose-6-phosphate An ester of glucose with phosphoric acid, made in the course of glucose metabolism by mammalian and other cells. It is a normal constituent of resting muscle and probably is in constant equilibrium with fructose-6-phosphate. Gluconeogenesis:
      • Hexokinase Hexokinase An enzyme that catalyzes the conversion of ATP and a d-hexose to ADP and a d-hexose 6-phosphate. D-glucose, d-mannose, d-fructose, sorbitol, and d-glucosamine can act as acceptors; ITP and dATP can act as donors. The liver isoenzyme has sometimes been called glucokinase. Glycolysis in the muscle 
      • Glucokinase in the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy 
    • Source of phosphate Phosphate Inorganic salts of phosphoric acid. Electrolytes group: adenosine Adenosine A nucleoside that is composed of adenine and d-ribose. Adenosine or adenosine derivatives play many important biological roles in addition to being components of DNA and RNA. Adenosine itself is a neurotransmitter. Class 5 Antiarrhythmic Drugs triphosphate (ATP)
  • Glucose-6-phosphate Glucose-6-phosphate An ester of glucose with phosphoric acid, made in the course of glucose metabolism by mammalian and other cells. It is a normal constituent of resting muscle and probably is in constant equilibrium with fructose-6-phosphate. Gluconeogenesis is then converted to glucose-1-phosphate by the enzyme phosphoglucomutase. 
  • Glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance + ATP → glucose-6-phosphate Glucose-6-phosphate An ester of glucose with phosphoric acid, made in the course of glucose metabolism by mammalian and other cells. It is a normal constituent of resting muscle and probably is in constant equilibrium with fructose-6-phosphate. Gluconeogenesis → glucose-1-phosphate

Step 2

Reaction of glucose-1-phosphate with uridine triphosphate Uridine triphosphate Uridine 5′-(tetrahydrogen triphosphate). A uracil nucleotide containing three phosphate groups esterified to the sugar moiety. Purine and Pyrimidine Metabolism (UTP) to form an activated form of glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance:

  • Glucose-1-phosphate reacts with UTP to form an active form of glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance known as uridine diphosphate Uridine diphosphate A uracil nucleotide containing a pyrophosphate group esterified to C5 of the sugar moiety. Purine and Pyrimidine Metabolism glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance (UDP-glucose).
    • Enzyme: UDP-glucose pyrophosphorylase 
    • Inorganic pyrophosphate is released in the reaction.
  • Glucose-1-phosphate + UTP → UDP-glucose + pyrophosphate (PP)
Glycogen synthesis

Glycogen synthesis Synthesis Polymerase Chain Reaction (PCR) — Making the substrate Substrate A substance upon which the enzyme acts. Basics of Enzymes:
Formation of UDP-glucose which is an active form in glycogenesis

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Step 3

Formation of glycosidic bond Glycosidic bond Basics of Carbohydrates 

  • In this step, attachment of the UDP-glucose to the hydroxyl group to the free end of a glycogen chain occurs.
    • Enzyme: glycogen synthase (rate-limiting enzyme of glycogenesis)
    • Glycogenin:
      • Classified as a glycosyltransferase
      • Core protein of the preexisting glycogen molecule to which glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance (from UDP-glucose) attaches
      • Acts as a primer to the synthesis Synthesis Polymerase Chain Reaction (PCR) of glycogen
  • UDP is released in the process.
  • The chain is formed via alpha-1,4-glycosidic bonds.
Growing the glycogen chain

Growing the glycogen chain—step 3 of glycogenesis:
Uridine diphosphate Uridine diphosphate A uracil nucleotide containing a pyrophosphate group esterified to C5 of the sugar moiety. Purine and Pyrimidine Metabolism glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance (UDP-glucose) is attached to the hydroxyl group of an already-existing glycogen chain, releasing UDP in the process. The reaction is catalyzed by glycogen synthase, the key regulatory enzyme of glycogenesis.

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Step 4

Branching of glycogen:

  • When a chain contains approximately 8–10 glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance units, branching follows (removing the growing chain from the nonreducing end of the chain).
  • A different enzyme then “reattaches” to a neighboring chain via bonds between carbons 1 and 6 (alpha-1,6-glycosidic bond).
    • Enzyme: amylo-(1,4→1,6)-transglycosylase 
    • Glycogen chains grow as glycogen synthase adds glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance residues and additional branches are produced.
Branching of glycogen chain mediated by the branching enzyme

Branching of glycogen chain mediated by the branching enzyme

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Glycogenolysis

Definition

Breakdown of glycogen to release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology energy in between meals or after the depletion of glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance

Step 1

Breakdown of glycogen into glucose-1-phosphate:

  • Glycogen is broken down into glucose-1-phosphate by phosphorolysis.
    • Enzyme: glycogen phosphorylase (key regulatory enzyme in glycogenolysis)
    • The reaction catalyzed is similar to hydrolysis Hydrolysis The process of cleaving a chemical compound by the addition of a molecule of water. Proteins and Peptides, but a phosphate Phosphate Inorganic salts of phosphoric acid. Electrolytes group is used to cleave bonds instead of water.
  • Alpha-1,4-glycosidic bonds are broken from the terminal end to release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology glucose-1-phosphate.
Glycogen breakdown

Glycogen breakdown:
Conversion of glycogen to glucose-1-phosphate by the enzyme glycogen phosphorylase

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Step 2

Removal of alpha-1,6-glycosidic bonds (branches):

  • As glycogen is an extensively branched polymer, further processes follow to break the branches to release Release Release of a virus from the host cell following virus assembly and maturation. Egress can occur by host cell lysis, exocytosis, or budding through the plasma membrane. Virology more glucose-1-phosphate.
  • Phosphorylase hydrolyzes alpha-1,4-glycosidic bonds until only 4 glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance residues are left before the alpha-1,6 branch. 
  • Further breakdown proceeds with the debranching enzyme (with a transferase and glucosidase activity).
    • 3 of the 4 glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance residues are removed, leaving 1 molecule.
    • The 3-glucose molecule chain (from the branch) is reattached to the nonreducing end of the linear chain, catalyzed by glucan transferase.
    • The single remaining molecule (in the branch) is removed by the alpha-1,6 glucosidase by hydrolysis Hydrolysis The process of cleaving a chemical compound by the addition of a molecule of water. Proteins and Peptides.
  • The phosphorylase/debranching process repeats to generate glucose-1-phosphate for energy use.
Glycogenolysis (breakdown of bonds and debranching). Png

Glycogenolysis (breakdown of bonds and debranching):
Alpha-1,4-glycosidic bonds are broken from the terminal end, catalyzed by phosphorylase. The bonds between glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance residues (blue) are hydrolyzed, releasing glucose-1-phosphate. Phosphorylase hydrolyzes alpha-1,4-glycosidic bonds until only 4 glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance residues (orange) are left before the alpha-1,6 branch. The debranching enzyme (with a transferase and glucosidase activity) then acts on the remaining linked residues. Three of the 4 glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance residues (orange) are removed, leaving 1 molecule. The 3-glucose molecule chain (from the branch) is reattached to the nonreducing end of the linear chain, catalyzed by glucan transferase. The single remaining molecule (in the branch) is removed by the alpha-1,6 glucosidase by hydrolysis Hydrolysis The process of cleaving a chemical compound by the addition of a molecule of water. Proteins and Peptides, releasing the glucose-1-phosphate. Phosphorylase/debranching process repeats to generate glucose-1-phosphate for energy use.

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Step 3

Conversion of the released glucose-1-phosphate to glucose-6-phosphate Glucose-6-phosphate An ester of glucose with phosphoric acid, made in the course of glucose metabolism by mammalian and other cells. It is a normal constituent of resting muscle and probably is in constant equilibrium with fructose-6-phosphate. Gluconeogenesis:

  • Glucose-1-phosphate is converted to glucose-6-phosphate Glucose-6-phosphate An ester of glucose with phosphoric acid, made in the course of glucose metabolism by mammalian and other cells. It is a normal constituent of resting muscle and probably is in constant equilibrium with fructose-6-phosphate. Gluconeogenesis
  • Enzyme: phosphoglucomutase
  • Fate of glucose-6 phosphate Phosphate Inorganic salts of phosphoric acid. Electrolytes:
    • In the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy:
      • Glycogen degradation occurs to maintain BG.
      • Via a reaction catalyzed by glucose-6-phosphatase Glucose-6-phosphatase An enzyme that catalyzes the conversion of d-glucose 6-phosphate and water to d-glucose and orthophosphate. Gluconeogenesis, glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance is freed up from glucose-6-phosphate Glucose-6-phosphate An ester of glucose with phosphoric acid, made in the course of glucose metabolism by mammalian and other cells. It is a normal constituent of resting muscle and probably is in constant equilibrium with fructose-6-phosphate. Gluconeogenesis, releasing inorganic phosphate Phosphate Inorganic salts of phosphoric acid. Electrolytes.
    • In the muscle:
      • Glycogenolysis proceeds to provide energy for muscle contraction.
      • Glucose-1-phosphate is converted to glucose-6-phosphate Glucose-6-phosphate An ester of glucose with phosphoric acid, made in the course of glucose metabolism by mammalian and other cells. It is a normal constituent of resting muscle and probably is in constant equilibrium with fructose-6-phosphate. Gluconeogenesis, which go to glycolysis Glycolysis Glycolysis is a central metabolic pathway responsible for the breakdown of glucose and plays a vital role in generating free energy for the cell and metabolites for further oxidative degradation. Glucose primarily becomes available in the blood as a result of glycogen breakdown or from its synthesis from noncarbohydrate precursors (gluconeogenesis) and is imported into cells by specific transport proteins. Glycolysis.
      • There is no glucose-6-phosphatase Glucose-6-phosphatase An enzyme that catalyzes the conversion of d-glucose 6-phosphate and water to d-glucose and orthophosphate. Gluconeogenesis in muscle, so glycogen from the muscle does not help maintain BG.
  • Glycogen is also degraded in lysosomes Lysosomes A class of morphologically heterogeneous cytoplasmic particles in animal and plant tissues characterized by their content of hydrolytic enzymes and the structure-linked latency of these enzymes. The intracellular functions of lysosomes depend on their lytic potential. The single unit membrane of the lysosome acts as a barrier between the enzymes enclosed in the lysosome and the external substrate. The activity of the enzymes contained in lysosomes is limited or nil unless the vesicle in which they are enclosed is ruptured or undergoes membrane fusion. The Cell: Organelles (via alpha-glucosidase) but does not contribute to the maintenance of BG.
Glycogen breakdown — glycogen phosphorylase

Glycogen breakdown—glycogen phosphorylase:
Conversion of glucose-1-phosphate to glucose-6-phosphate Glucose-6-phosphate An ester of glucose with phosphoric acid, made in the course of glucose metabolism by mammalian and other cells. It is a normal constituent of resting muscle and probably is in constant equilibrium with fructose-6-phosphate. Gluconeogenesis by the enzyme phosphoglucomutase

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Regulation of Glycogen Metabolism

Regulation overview

  • Glycogen metabolism is controlled by allosteric (metabolites indicate the cellular energy state and help in modulation) and hormonal regulation
  • Hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types and different effectors coordinate to produce the appropriate effect necessary to meet the energy needs.
  • The main regulatory mechanism involved is phosphorylation Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Post-translational Protein Processing, affecting the 2 main enzymes Enzymes Enzymes are complex protein biocatalysts that accelerate chemical reactions without being consumed by them. Due to the body’s constant metabolic needs, the absence of enzymes would make life unsustainable, as reactions would occur too slowly without these molecules. Basics of Enzymes:
    • Glycogen phosphorylase (activated by phosphorylation Phosphorylation The introduction of a phosphoryl group into a compound through the formation of an ester bond between the compound and a phosphorus moiety. Post-translational Protein Processing)
    • Glycogen synthase (activated by dephosphorylation)
  • The regulating hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types include:
    • Insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin (promotes glycogenesis)
    • Glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions and epinephrine Epinephrine The active sympathomimetic hormone from the adrenal medulla. It stimulates both the alpha- and beta- adrenergic systems, causes systemic vasoconstriction and gastrointestinal relaxation, stimulates the heart, and dilates bronchi and cerebral vessels. Sympathomimetic Drugs (promote glycogenolysis)

Regulation of glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions degradation

Glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions and epinephrine Epinephrine The active sympathomimetic hormone from the adrenal medulla. It stimulates both the alpha- and beta- adrenergic systems, causes systemic vasoconstriction and gastrointestinal relaxation, stimulates the heart, and dilates bronchi and cerebral vessels. Sympathomimetic Drugs activate adenylate cyclase in the cell membrane Cell Membrane A cell membrane (also known as the plasma membrane or plasmalemma) is a biological membrane that separates the cell contents from the outside environment. A cell membrane is composed of a phospholipid bilayer and proteins that function to protect cellular DNA and mediate the exchange of ions and molecules. The Cell: Cell Membrane via G proteins Proteins Linear polypeptides that are synthesized on ribosomes and may be further modified, crosslinked, cleaved, or assembled into complex proteins with several subunits. The specific sequence of amino acids determines the shape the polypeptide will take, during protein folding, and the function of the protein. Energy Homeostasis.

  • 3’,5’-cyclic adenosine monophosphate Adenosine monophosphate Adenine nucleotide containing one phosphate group esterified to the sugar moiety in the 2′-, 3′-, or 5′-position. Purine and Pyrimidine Metabolism ( cAMP cAMP An adenine nucleotide containing one phosphate group which is esterified to both the 3′- and 5′-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and acth. Phosphodiesterase Inhibitors):
    • Formed when adenylate cyclase converts ATP to cAMP cAMP An adenine nucleotide containing one phosphate group which is esterified to both the 3′- and 5′-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and acth. Phosphodiesterase Inhibitors
    • Activates protein kinase Protein kinase A family of enzymes that catalyze the conversion of ATP and a protein to adp and a phosphoprotein. Interferons A (PKA)
  • PKA:
    • Phosphorylates glycogen synthase (making it less active), thus decreasing glycogen synthesis Synthesis Polymerase Chain Reaction (PCR)
    • Phosphorylates phosphorylase kinase → activating glycogen phosphorylase b to phosphorylase a → increasing glycogenolysis
  • In the muscle:
    • Calcium Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Electrolytes (Ca²⁺): activates phosphorylase kinase (which activates phosphorylase b to a)
    • Adenosine monophosphate Adenosine monophosphate Adenine nucleotide containing one phosphate group esterified to the sugar moiety in the 2′-, 3′-, or 5′-position. Purine and Pyrimidine Metabolism (AMP):
      • During muscle contraction: ATP → ADP → AMP
      • ↑ AMP stimulates glycogenolysis by converting phosphorylase b to phosphorylase a

Regulation of glycogen synthesis Synthesis Polymerase Chain Reaction (PCR)

  • After a meal → ↑ insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin, ↓ glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions
    • A fed state Fed state Energy Homeostasis does not activate cAMP cAMP An adenine nucleotide containing one phosphate group which is esterified to both the 3′- and 5′-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and acth. Phosphodiesterase Inhibitors cascade (in effect, protein kinase Protein kinase A family of enzymes that catalyze the conversion of ATP and a protein to adp and a phosphoprotein. Interferons is inactive).
    •  ↑ Insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin activates phosphatases Phosphatases Oxazolidinones:
      • Dephosphorylates phosphorylase kinase and phosphorylase a, making them inactive
      • Dephosphorylates glycogen synthase, which activates the enzyme and, in effect, increases glycogen synthesis Synthesis Polymerase Chain Reaction (PCR)
  • In the muscle:
    • After a meal: ↓ cAMP cAMP An adenine nucleotide containing one phosphate group which is esterified to both the 3′- and 5′-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and acth. Phosphodiesterase Inhibitors, AMP, and Ca²⁺
    • Insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin also facilitates transport of glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance into muscle cells, increasing glycogen synthesis Synthesis Polymerase Chain Reaction (PCR).

Hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types and glycogen metabolism

Table: Hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types and glycogen metabolism
Hormone Glycogenesis Glycogenolysis Serum Glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance
Insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin Activation Inhibition Decreases
Glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions Inhibition Activation Increases
Epinephrine Epinephrine The active sympathomimetic hormone from the adrenal medulla. It stimulates both the alpha- and beta- adrenergic systems, causes systemic vasoconstriction and gastrointestinal relaxation, stimulates the heart, and dilates bronchi and cerebral vessels. Sympathomimetic Drugs Inhibition Activation Increases

Glycogen metabolism and regulating mechanisms

Table: Effectors of glycogen metabolism and regulating mechanisms
Effectors Glycogenolysis Glycogenesis
cAMP cAMP An adenine nucleotide containing one phosphate group which is esterified to both the 3′- and 5′-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and acth. Phosphodiesterase Inhibitors
PK
AMP (muscle)
Calcium Calcium A basic element found in nearly all tissues. It is a member of the alkaline earth family of metals with the atomic symbol ca, atomic number 20, and atomic weight 40. Calcium is the most abundant mineral in the body and combines with phosphorus to form calcium phosphate in the bones and teeth. It is essential for the normal functioning of nerves and muscles and plays a role in blood coagulation (as factor IV) and in many enzymatic processes. Electrolytes/muscle contraction
cAMP cAMP An adenine nucleotide containing one phosphate group which is esterified to both the 3′- and 5′-positions of the sugar moiety. It is a second messenger and a key intracellular regulator, functioning as a mediator of activity for a number of hormones, including epinephrine, glucagon, and acth. Phosphodiesterase Inhibitors: cyclic adenosine monophosphate Adenosine monophosphate Adenine nucleotide containing one phosphate group esterified to the sugar moiety in the 2′-, 3′-, or 5′-position. Purine and Pyrimidine Metabolism
PK: protein kinase Protein kinase A family of enzymes that catalyze the conversion of ATP and a protein to adp and a phosphoprotein. Interferons
AMP: adenosine monophosphate Adenosine monophosphate Adenine nucleotide containing one phosphate group esterified to the sugar moiety in the 2′-, 3′-, or 5′-position. Purine and Pyrimidine Metabolism
Table: Hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types of glycogen metabolism and regulating mechanisms
Hormones Hormones Hormones are messenger molecules that are synthesized in one part of the body and move through the bloodstream to exert specific regulatory effects on another part of the body. Hormones play critical roles in coordinating cellular activities throughout the body in response to the constant changes in both the internal and external environments. Hormones: Overview and Types Glycogenolysis Glycogenesis
Insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin
Glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions
Epinephrine Epinephrine The active sympathomimetic hormone from the adrenal medulla. It stimulates both the alpha- and beta- adrenergic systems, causes systemic vasoconstriction and gastrointestinal relaxation, stimulates the heart, and dilates bronchi and cerebral vessels. Sympathomimetic Drugs
Table: Regulatory enzyme of glycogen metabolism and regulating mechanisms
Regulatory Enzyme Glycogenolysis Glycogenesis
Glycogen synthase Activated (enzyme is phosphorylated) Inactivated
Glycogen synthase Inactivated Activated (enzyme is dephosphorylated)
Glycogen metabolism diagram

Glycogen metabolism and regulatory factors:
Epinephrine Epinephrine The active sympathomimetic hormone from the adrenal medulla. It stimulates both the alpha- and beta- adrenergic systems, causes systemic vasoconstriction and gastrointestinal relaxation, stimulates the heart, and dilates bronchi and cerebral vessels. Sympathomimetic Drugs, glucagon Glucagon A 29-amino acid pancreatic peptide derived from proglucagon which is also the precursor of intestinal glucagon-like peptides. Glucagon is secreted by pancreatic alpha cells and plays an important role in regulation of blood glucose concentration, ketone metabolism, and several other biochemical and physiological processes. Gastrointestinal Secretions, and AMP activate glycogen phosphorylase, thus glycogenolysis is promoted, producing glucose Glucose A primary source of energy for living organisms. It is naturally occurring and is found in fruits and other parts of plants in its free state. It is used therapeutically in fluid and nutrient replacement. Lactose Intolerance for energy consumption. Insulin Insulin Insulin is a peptide hormone that is produced by the beta cells of the pancreas. Insulin plays a role in metabolic functions such as glucose uptake, glycolysis, glycogenesis, lipogenesis, and protein synthesis. Exogenous insulin may be needed for individuals with diabetes mellitus, in whom there is a deficiency in endogenous insulin or increased insulin resistance. Insulin activates glycogen synthase, facilitating glycogen buildup.

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Clinical Relevance

Glycogen storage disease Glycogen storage disease A group of inherited metabolic disorders involving the enzymes responsible for the synthesis and degradation of glycogen. In some patients, prominent liver involvement is presented. In others, more generalized storage of glycogen occurs, sometimes with prominent cardiac involvement. Benign Liver Tumors: a group of inherited disorders characterized by abnormalities in glycogen metabolism, resulting in an abnormal accumulation of glycogen in the tissues.

Table: Glycogen storage diseases Glycogen Storage Diseases A group of inherited metabolic disorders involving the enzymes responsible for the synthesis and degradation of glycogen. In some patients, prominent liver involvement is presented. In others, more generalized storage of glycogen occurs, sometimes with prominent cardiac involvement. Benign Liver Tumors
Type Diseases Enzyme Deficiency Clinical Features
0 Lewis disease Glycogen synthase
  • Hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia
  • Hyperketonemia
  • Early mortality Mortality All deaths reported in a given population. Measures of Health Status
Von Gierke disease Glucose-6-phosphatase Glucose-6-phosphatase An enzyme that catalyzes the conversion of d-glucose 6-phosphate and water to d-glucose and orthophosphate. Gluconeogenesis
  • Glycogen accumulation Glycogen Accumulation Cellular Accumulations in the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy and renal tubule cells
  • Hepatomegaly
  • Hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia
  • Lactic acidosis Acidosis A pathologic condition of acid accumulation or depletion of base in the body. The two main types are respiratory acidosis and metabolic acidosis, due to metabolic acid build up. Respiratory Acidosis
  • Ketosis Ketosis A condition characterized by an abnormally elevated concentration of ketone bodies in the blood (acetonemia) or urine (acetonuria). It is a sign of diabetes complication, starvation, alcoholism or a mitochondrial metabolic disturbance (e.g., maple syrup urine disease). Hyperglycemic Crises
  • Hyperlipidemia (HLD)
Pompe disease Lysosomal α-1,4 and α-1,6 glucosidase (acid maltase Maltase Digestion and Absorption of Carbohydrates)
  • Lysosomal accumulation of glycogen
  • Heart failure Heart Failure A heterogeneous condition in which the heart is unable to pump out sufficient blood to meet the metabolic need of the body. Heart failure can be caused by structural defects, functional abnormalities (ventricular dysfunction), or a sudden overload beyond its capacity. Chronic heart failure is more common than acute heart failure which results from sudden insult to cardiac function, such as myocardial infarction. Total Anomalous Pulmonary Venous Return (TAPVR) (HF)
  • Cardiomyopathy Cardiomyopathy Cardiomyopathy refers to a group of myocardial diseases associated with structural changes of the heart muscles (myocardium) and impaired systolic and/or diastolic function in the absence of other heart disorders (coronary artery disease, hypertension, valvular disease, and congenital heart disease). Cardiomyopathy: Overview and Types (CM)
  • Muscle hypotonia Hypotonia Duchenne Muscular Dystrophy and dystrophy
  • Early mortality Mortality All deaths reported in a given population. Measures of Health Status
Forbes-Cori disease Debranching enzyme (amylo-1,6-glucosidase)
  • Fasting hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia
  • Hepatomegaly
  • Myopathy Myopathy Dermatomyositis
  • Stunted growth
Andersen disease Andersen disease An autosomal recessive metabolic disorder due to a deficiency in expression of glycogen branching enzyme 1 (alpha-1, 4-glucan-6-alpha-glucosyltransferase), resulting in an accumulation of abnormal glycogen with long outer branches. Clinical features are muscle hypotonia and cirrhosis. Death from liver disease usually occurs before age 2. Glycogen Storage Disorders 1,4-α-glucan branching enzyme
  • Accumulation of abnormal glycogen
  • Hepatosplenomegaly Hepatosplenomegaly Cytomegalovirus
  • Neuromuscular presentation
  • Death from HF or liver failure Liver failure Severe inability of the liver to perform its normal metabolic functions, as evidenced by severe jaundice and abnormal serum levels of ammonia; bilirubin; alkaline phosphatase; aspartate aminotransferase; lactate dehydrogenases; and albumin/globulin ratio. Autoimmune Hepatitis
McArdle disease Muscle phosphorylase
Hers disease Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy phosphorylase
  • Hepatomegaly
  • Glycogen accumulation Glycogen Accumulation Cellular Accumulations in the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy
  • Mild hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia
Tarui disease Tarui disease An autosomal recessive glycogen storage disease in which there is deficient expression of 6-phosphofructose 1-kinase in muscle resulting in abnormal deposition of glycogen in muscle tissue. These patients have severe congenital muscular dystrophy and are exercise intolerant. Glycogen Storage Disorders Muscle phosphofructokinase (PFK)
  • Poor exercise tolerance Tolerance Pharmacokinetics and Pharmacodynamics
  • Low blood lactate post-exercise
  • Hemolytic anemia Anemia Anemia is a condition in which individuals have low Hb levels, which can arise from various causes. Anemia is accompanied by a reduced number of RBCs and may manifest with fatigue, shortness of breath, pallor, and weakness. Subtypes are classified by the size of RBCs, chronicity, and etiology. Anemia: Overview and Types ( HA HA Hemolytic anemia (HA) is the term given to a large group of anemias that are caused by the premature destruction/hemolysis of circulating red blood cells (RBCs). Hemolysis can occur within (intravascular hemolysis) or outside the blood vessels (extravascular hemolysis). Hemolytic Anemia)
Hepatic phosphorylase kinase deficiency Phosphorylase kinase deficiency Glycogen Storage Disorders Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy phosphorylase kinase
  • Hepatomegaly
  • Glycogen accumulation Glycogen Accumulation Cellular Accumulations in the liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy
  • Mild hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia
Phosphorylase kinase deficiency Phosphorylase kinase deficiency Glycogen Storage Disorders Liver Liver The liver is the largest gland in the human body. The liver is found in the superior right quadrant of the abdomen and weighs approximately 1.5 kilograms. Its main functions are detoxification, metabolism, nutrient storage (e.g., iron and vitamins), synthesis of coagulation factors, formation of bile, filtration, and storage of blood. Liver: Anatomy and muscle phosphorylase kinase
  • Hepatomegaly
  • Hypoglycemia Hypoglycemia Hypoglycemia is an emergency condition defined as a serum glucose level ≤ 70 mg/dL (≤ 3.9 mmol/L) in diabetic patients. In nondiabetic patients, there is no specific or defined limit for normal serum glucose levels, and hypoglycemia is defined mainly by its clinical features. Hypoglycemia
  • Exercise intolerance
PGAM deficiency Phosphoglycerate mutase Phosphoglycerate mutase An enzyme that catalyzes the conversion of 2-phospho-d-glycerate to 3-phospho-d-glycerate. Glycolysis
ⅩⅠ Lactate dehydrogenase Lactate Dehydrogenase Osteosarcoma A deficiency Lactate dehydrogenase Lactate Dehydrogenase Osteosarcoma A
  • Fatigability
  • Myoglobinuria Myoglobinuria The presence of myoglobin in urine usually as a result of rhabdomyolysis. Rhabdomyolysis
  • Rhabdomyolysis Rhabdomyolysis Rhabdomyolysis is characterized by muscle necrosis and the release of toxic intracellular contents, especially myoglobin, into the circulation. Rhabdomyolysis
XII Aldolase A deficiency Aldolase A deficiency Glycogen Storage Disorders Aldolase Aldolase Becker Muscular Dystrophy A
  • Myoglobinuria Myoglobinuria The presence of myoglobin in urine usually as a result of rhabdomyolysis. Rhabdomyolysis
  • Hemolysis
  • Jaundice Jaundice Jaundice is the abnormal yellowing of the skin and/or sclera caused by the accumulation of bilirubin. Hyperbilirubinemia is caused by either an increase in bilirubin production or a decrease in the hepatic uptake, conjugation, or excretion of bilirubin. Jaundice
  • Fatigability
  • Rhabdomyolysis Rhabdomyolysis Rhabdomyolysis is characterized by muscle necrosis and the release of toxic intracellular contents, especially myoglobin, into the circulation. Rhabdomyolysis
XIII Beta-enolase deficiency Beta-enolase deficiency Glycogen Storage Disorders (muscle) Beta-enolase
  • Rhabdomyolysis Rhabdomyolysis Rhabdomyolysis is characterized by muscle necrosis and the release of toxic intracellular contents, especially myoglobin, into the circulation. Rhabdomyolysis
  • Exercise intolerance
XIV Phosphoglucomutase I deficiency (muscle) Phosphoglucomutase I
  • Exercise intolerance
  • Rhabdomyolysis Rhabdomyolysis Rhabdomyolysis is characterized by muscle necrosis and the release of toxic intracellular contents, especially myoglobin, into the circulation. Rhabdomyolysis
  • Myoglobinuria Myoglobinuria The presence of myoglobin in urine usually as a result of rhabdomyolysis. Rhabdomyolysis
XV Glycogenin I deficiency (muscle) Glycogenin I
  • Arrhythmias
  • Muscle weakness
Fanconi-Bickel syndrome GLUT2 GLUT2 A glucose transport facilitator that is expressed primarily in pancreatic beta cells; liver; and kidneys. It may function as a glucose sensor to regulate insulin release and glucose homeostasis. Digestion and Absorption
PGAM: Phosphoglycerate mutase Phosphoglycerate mutase An enzyme that catalyzes the conversion of 2-phospho-d-glycerate to 3-phospho-d-glycerate. Glycolysis
GLUT2 GLUT2 A glucose transport facilitator that is expressed primarily in pancreatic beta cells; liver; and kidneys. It may function as a glucose sensor to regulate insulin release and glucose homeostasis. Digestion and Absorption: Glucose transporter 2 Glucose transporter 2 A glucose transport facilitator that is expressed primarily in pancreatic beta cells; liver; and kidneys. It may function as a glucose sensor to regulate insulin release and glucose homeostasis. Digestion and Absorption of Carbohydrates

References

  1. Berg, JM, Tymoczko, JL, & Stryer, L. (Eds.). (2002). Glycogen Metabolism. In Berg, JM, et al. (Eds.), Biochemistry (5th ed.). WH Freeman. https://www.ncbi.nlm.nih.gov/books/NBK21190/
  2. Craigen, W, Darras, B. (2019). Overview of inherited disorders of glucose and glycogen metabolism. UpToDate. Retrieved Oct 30, 2021 from https://www.uptodate.com/contents/overview-of-inherited-disorders-of-glucose-and-glycogen-metabolism
  3. Le, T, Bhushan, V, & Sochat, M. (Eds.). (2021). “ Biochemistry—metabolism. In Le, T, at al. (Ed.), First Aid for USMLE Step 1 (pp. 86–87).
  4. Murray, R, Granner, D, Rodwell, V. (2006). Metabolism of glycogen. In Murray, R., et al. (Eds.), Harper’s Illustrated Biochemistry (27th ed., pp. 159–166).
  5. Swanson, T, Kim, S, & Glucksman, M. (2010). Glycogen metabolism. In Swanson, T, et al. (Eds.), Biochemistry, Molecular Biology and Genetics (5th ed., pp. 97–104). Lippincott, Williams & Wilkins.

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