Question

What do you think would happen if the enzyme that converted maleate to oxalocaetate were inhibited? What molecule would build up? What molecule would be depleted? Would this effect glycolysis? Would this effect oxidative phosphorylation?

Answer 1

• Malate dehydrogenase catalyzes the “last step” of the TCA cycle, the conversion of malate to oxaloacetate, with the production of the final NADH. The malate dehydrogenase reaction in “reverse” allows the direct conversion of oxaloacetate to malate; this is important because malate can be transported out of the mitochondria, while oxaloacetate cannot. If Malate dehydrogenase enzymes were inhibited then malate cannot be transported out of the mitochondria and concentration of malate will be increased.
• Malate would be build up and oxaloacetate formation will be affected.
• No effect on glycolysis because glycolysis pathway is before TCA cycle.
• Most of the free energy released during the oxidation of glucose to co₂ is retained in the reduced coenzymes NADH and FADH₂, generated during glycolysis and TCA cycle. The larger amount of free energy released during the oxidation of NADH and FADH₂ is used in the formation of ATP. Thus this energy conversion process will be affected.