Some regulatory properties of 3-hydroxybutyrate dehydrogenase in frozen-thawed rat liver mitochondria.

The influence of various organic acids on 3-hydroxybutyrate dehydrogenase activity in frozen-thawed rat liver mitochondria was studied. Pyruvate and oxaloacetate were found to exert inhibitory effects, that were apparently indirect ones. Malonate appeared to be a competitive inhibitor of the enzyme, the kinetic constants being comparable with those for enzyme preparations from other sources. Physiological role for malonate and oxaloacetate in the ketone body oxidation are discussed.