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 localised to the mitochondrial matrix. Acetyl‐CoA hydrolase has an apparent Km for acetyl‐CoA of 51 μM, and a specific activity at 30 °C of 870 nmol of acetate formed/min per mg 100000 × g supernatant protein. The enzyme is noncompetitively activated by ADP and inhibited by NADH and the effect of these nucleotides may well 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 °C. The energy of activation is 12200 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 as well as at normal body temperature is discussed. Copyright © 1976, Wiley Blackwell. All rights reserved