Purification and characterization of a long-chain acyl-CoA hydrolase from rat liver microsomes

A long-chain acyl-CoA hydrolase from rat liver microsomes has been purified by solvent extraction and gel chromatography to homogeneity as judged by polyacrylamide gel electrophoresis in the presence and absence of sodium dodecyl sulfate. The enzyme was a monomer of molecular weight 59 000. In a sucrose gradient it sedimented at 4.3 S. The isoelectric point, pI was 6.9, and the Stokes radius was approx. 31 A. The enzyme hydrolyzed long-chain fatty acyl-CoA (C7--C18) with maximum activity for palmitoyl-CoA. Bovine serum albumin activation of the enzyme was related to the ratio acyl-CoA/bovine serum albumin, and at high ratios, acyl-CoA inhibited the enzyme activity. Disregarding the substrate inhibition, an apparent Km of 65 nmol/mg protein or 1-10(-7) M and a V of 750 nmol/mg protein per min were calculated. The enzyme was inhibited by p-hydroxymercuribenzoate and N-ethylmaleimide. Reactivation by means of dithiothreitol was not complete.