[Characterization of the kinase activity of bovine adrenal pyruvate dehydrogenase complex]

In the presence of [gamma-32P]ATP the bovine adrenal pyruvate dehydrogenase complex accepts the label simultaneously and becomes inactivated. This suggests the existence of kinase in the composition of the complex as is typical of the complexes from other animal sources. The Pi is incorporated into the subunit with molecular weight of 42 000. The kinase activity of the adrenal pyruvate dehydrogenase complex is high: within the first 20 sec of incubation with ATP the inactivation is as high as 60%. The pH optimum for kinase is around 7.3. The apparent Km value for ATP with 50 mM KCl is 7 microM; that in the absence of KCl is 10 microM. ADP is a competitive inhibitor of kinase with respect to ATP (Ki = 100 microM), when K+ are present in the medium. Thiamine pyrophosphate and pyruvate decrease the rate of pyruvate dehydrogenase complex inactivation.