Role of Kinase a and Effect of Insulin

by Kevin Ahern, PhD

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    00:01 The coordinated pathway control that happens as a result of epinephrine action.

    00:05 Actually happens through this enzyme known as protein kinase A, that you have seen several times now.

    00:11 So I have summarized the activities of protein kinase A with respect to its action on other enzymes and what the result of those actions is. So let's step through these slides.

    00:22 We see the epinephrine glucagon stimulation which, of course, makes the cyclic AMP that makes the protein kinase A active.

    00:30 The active form of protein kinase A does the following things and yes it's a very busy enzyme.

    00:36 It takes the phosphorylase kinase and makes it active.

    00:42 Phosphorylase kinase in turn makes glycogen phosphorylase active which favors glycogen breakdown. So glucose is released.

    00:52 Protein kinase A, phosphorylates the glycogen synthase and causes it to become inactive, so the glucose is saved; because, glucose isn't being used to make glycogen.

    01:04 Protein kinase A phosphorylates fructose bisphosphatase 2, which favors the gluconeogenesis pathway; because, it favors the removal of phosphates from F2,6BP.

    01:20 Protein kinase A inhibits the PFK 2 for the same reason, by putting a phosphate onto that yin and yang enzyme. Glycolysis is inhibited and glucose is safe.

    01:33 And then protein kinase A also works on the triacylglycerol lipase.

    01:38 When it does that it favors the breakdown of fat and triacylglycerol lipase has another effect ultimately on acetyl-CoA-carboxylase.

    01:48 This favors the inactivation of that enzyme so that fatty acid synthesis is stop.

    01:53 So to summarize we can see that what this protein kinase A is doing, is favoring again the reciprocal regulation.

    01:59 It's stopping glycogen synthesis as it's favoring glycogen breakdown.

    02:03 Glucose concentrations in the body get increased.

    02:07 In the case of glycolysis and gluconeogenesis, gluconeogenesis is being in favored and glycolysis is being inhibited.

    02:13 Again for the production of glucose for the body that needs glucose.

    02:19 Third, with respect to fat, protein kinase A is favoring fats being broken down to release fatty acids for the body so it has the energy that it needs.

    02:30 Now this means in simple terms that protein kinase A is increasing glucose.

    02:36 It's increasing glucose and it's increasing fatty acids.

    02:40 All of these are necessary for the body to have the energy that it needs and all of these are happening when the body needs the energy.

    02:48 Thus protein kinase A is making fuel available for the body for making ATP; because, the breakdown of glucose and the breakdown of fatty acids is the way that the body makes ATP.

    03:02 We have seen what happens with the epinephrine. Now, let's take a look at what happens when insulin stimulates the cells.

    03:06 We have seen before that insulin stimulation favors the activation of phosphoprotein phosphatase.

    03:13 And phosphoprotein phosphatase has the opposite affects of all these things we saw with respect to the pathways of epinephrine.

    03:20 Glucose synthesis is activated and glucose is used. Meaning that glycogen breakdown is not occurring and no glucose is being released.

    03:28 In the case of glycolysis and gluconeogenesis, glycolysis is activated and glucose is being used.

    03:35 Gluconeogenesis is inhibited and no glucose is being made.

    03:38 Now in the case of fats and fatty acid, this is a little bit more complicated.

    03:42 Fatty acid synthesis is being activated but it's being converted into fat.

    03:47 So those fatty acids are being used and their concentration is reduced.

    03:52 And that's happening also because the fat breakdown is being inhibited.

    03:56 So what we see in the result of these actions then is that glucose is decreasing.

    04:00 Glucose is decreasing and ultimately fatty acids are decreasing as well; because, they are being used.

    04:05 This means that the body is taking and storing chemical energy using all the stuff that's floating around.

    About the Lecture

    The lecture Role of Kinase a and Effect of Insulin by Kevin Ahern, PhD is from the course Metabolic Control.

    Included Quiz Questions

    1. Phosphorylase kinase
    2. FBPase2
    3. Glycogen synthase
    4. PFK2
    5. Acetyl CoA carboxylase
    1. Phosphoprotein phosphatase
    2. Phosphorylase kinase
    3. FBPase2
    4. PFK2
    5. Acetyl CoA carboxylase

    Author of lecture Role of Kinase a and Effect of Insulin

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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