Role of dehydrogenase competition in metabloic regulation. The case of lactate and alpha-glycerophosphate dehydrogenases.

Many tissues expressing capacities for both anaerobic and aerobic glycolysis contain significant amounts of both lactate dehydrogenase and alpha-glycerophosphate dehydrogenase. Since the first serves in oxidation-reduction balance during anaerobic metabolism, while the second serves in the alpha-glycerophosphate cycle during aerobic metabolism, a provision seemed to be made (through competition for coenzyme) to encourage relatively exclusive function of either one or the other dehydrogenase. Competition for coenzyme was found to depend upon the isoenzyme form of each dehydrogenase (which determines the sensitivity of each reaction to modulators) and the concentration of two key metabolites, alpha-glycerophosphate and creatine phosphate, which differentially influence alpha-glycerophosphate dehydrogenases and lactate dehydrogenases. The sensitivities of various dehydrogenase isoenzymes to these modulators correlated well with their expected roles in the tissue of origin.