[Inhibition of kinase activity of the adrenal pyruvate dehydrogenase complex by the mitochondrial component]

A component inhibiting the phosphorylation-linked inactivation of the adrenal pyruvate dehydrogenase complex in the presence of ATP was revealed during purification of the complex from bovine adrenal mitochondria. The degree of the kinase activity inhibition is greater at lower concentrations of ATP. It was assumed that the mitochondrial component screens the kinase active site or the phosphorylation sites of pyruvate dehydrogenase, thus limiting the ATP access to them. Proteins and lipids are incorporated into the component at a ratio 2:1, which is suggestive of its lipoprotein nature. The effect of the mitochondrial component on the kinase activity of the pyruvate dehydrogenase complex is somewhat specific and is unaffected by bovine serum albumin or blood serum lipoproteins.