Question

2. a. explain how a mutation in pyruvate dehydrogenase kinase that increases the enzymes Km will affect the activity of the complex pyruvate dehydrogenase?

b. explain how pyruvate dehydrogenase complex is controlled during physical activity by PDP?

c. how can a mutation that affects the binding sight of calcium ions on the pdp enzyme affect the activity of phosphatase enzyme?

and how is it likely to affect pdc during physical activity?

Answer 1

Please find the answers below:

Answer a: Pyruvade dehydrogen complex or pdc represents a set of enzymes utilized for channelizing the products of glycolysis to citric acid cycle. It is a very well known fact that the Km represents the substrate concentration at which the reaction rate of an enzyme catalyzed reaction is half of its maximum. If a mutation increases the Km for the enzyme, more substrate would be required to achieve the maximum possible reaction rate. Hence, the overall rate of reaction would decrease.

Answer b: The pdc is involved in bridging between glycolysis and citric acid cycle so that enery production secondary to aerobic respiration could be maximized. During physical activity, the oxygen consumption of the body increases and hence the activity of pdc is expected to increase proportionately. Importantly, oxidized pdc enzyme is known to undergo non-biological function and hence, the active site of the pdc is protected from over-oxidation during strenous exercise. As the intensity of exercise decreases, the enzyme stablizes itself and activity resumes.

Answer c: Since the calcium ions are necessarily required for controlling the conformational changes in the pdp enzyme when appropriate substrate is present, a mutation resulting in failure of this binding would result in protein misfolding and hence failure to achieve the appopriate structural complex. Consequently, the enzyme function would cease to proceed as normal.