Acetyl‐CoA Hydrolase; Activity, Regulation and Physiological, Significance of the Enzyme in Brown Adipose Tissue from Hamster

Abstract

Acetate production in hamster brown adipose tissue is a consequence of the existence of an acetyl-CoA hydrolase. The enzyme is soluble and is localized to the mitochondrial matrix. Acetyl-CoA hydrolase has an apparent Km for acetyl-CoA of 51 .mu.M and a specific activity at 30.degree. C of 870 nmol of acetate formed/min per mg 100,000 .times. g supernatant protein. The enzyme is noncompetitively activated by ADP and inhibited by NADH and the effect of these nucleotides may serve to regulate the enzyme activity in vivo. A strong product inhibition by CoA is observed. The inhibition is of S-linear-I-hyperbolic noncompetitive nature. The hydrolase has a Q10 of 2.0, which represents a 7.3% change in the rate of acetate production per degrees centigrade. The energy of activation is 12,200 cal/mol (53,905 J/mol). The regulatory role of acetyl-CoA hydrolase for fatty acid oxidation in brown adipose tissue of the hamster (a hibernator) at low and at normal body temperature is discussed.