Glycolysis: Dhap –> Ga3-P – Glycolysis and Pyruvate Metabolism

by Kevin Ahern, PhD

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    00:00 This is a reaction that students of biochemistry frequently like a lot and the reason that they like this reaction is because dihydroxyacetone phosphate is becoming converted into the other product of the previous reaction glyceraldehyde-3-phosphate. When this happens we then have 2 of every molecule that continues down the pathway of glycolysis.

    00:21 This way students don't have to learn one pathway for the dihydroxyacetone phosphate.

    00:26 and a different pathway for the glyceraldehyde-3-phosphate. We simply have two glyceraldehyde-3-phosphates to follow.

    00:32 The enzyme that catalyzes this reaction is called triose phosphate isomerase and as an example of what we call a perfect enzyme. Now in one of the other lectures that I have given, I have described what perfect enzymes are. But perfect enzymes are enzymes that catalyze reactions amazingly efficiently, amazingly rapidly with amazingly little material.

    00:56 The reason of this enzyme does this here is because there is an intermediate its in the process of making the glyceraldehyde-3-phosphate that is extraordinary unstable.

    01:08 If that intermediate sits around for any period of time it will fall apart and this reaction will not occur. So to keep that from happening, this enzyme has evolved to be very very rapid in its turnover.

    01:20 So this reaction is also one of these readily reversible reactions. It doesn't matter too much to the cell which way it goes and the direction that it goes is gonna be a function of the concentration of the intermediates.

    01:31 As you might imagine, this reaction can be reversed in the process of gluconeogenesis.

    01:37 So the delta G zero prime is a little positive but it is not excessive for cell to overcome.

    01:43 This as I noted is a diffusion limited enzyme and I will remind you that the diffusion limited enzyme is one who's rate of reaction relies only on the rate with which the substrates can diffuse into the active site.

    About the Lecture

    The lecture Glycolysis: Dhap –> Ga3-P – Glycolysis and Pyruvate Metabolism by Kevin Ahern, PhD is from the course Carbohydrate Metabolism.

    Included Quiz Questions

    1. The triosephosphate isomerase enzyme catalyzes the reversible interconversions of 1,3-bisphosphoglycerate and 3-phosphoglycerate in the glycolysis pathway
    2. The TPI enzyme is a dimer of identical subunits
    3. The TPI deficiencies are related to progressive, severe neurological disorders and chronic hemolytic anemia
    4. The TPI enzyme falls under the category of diffusion-limited enzymes because it is limited only by the rate of diffusion of substrate molecules into and out of the active site of the enzyme
    5. The enzyme TPI is an example of the catalytically perfect enzyme as it catalyzes the reactions with high efficiency at high rates at low substrate concentrations

    Author of lecture Glycolysis: Dhap –> Ga3-P – Glycolysis and Pyruvate Metabolism

     Kevin Ahern, PhD

    Kevin Ahern, PhD

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