[Regulators of 3-hydroxybutyrate dehydrogenase activity in rat liver mitochondria].

Effects of numerous organic acids on the 3-hydroxybutyrate dehydrogenase activity were studied in isolated rat liver mitochondria with nonspecific permeability. Amino acids, most of citric acid cycle intermediates, lactate, maleate, acetate, glycerol-3-phosphate, urea, palmitate, and phosphoenolpyruvate plus ADP were shown to modify the enzyme activity insignificantly. The inhibitory effect of pyruvate seems to be a result of the concomitant cytosolic lactate dehydrogenase activity, and the effect of oxaloacetate is that of the mitochondrial matrix malate dehydrogenase activity. Malonate proves to be a competitive inhibitor of the 3-hydroxybutyrate dehydrogenase activity, enzyme affinity for malonate being the same irrespective of the source or purification of the preparation.