Physiochemical properties of the long-chain-acyl-CoA hydrolase from rat liver microsomes

The physicochemical properties of a long-chain-acyl-CoA hydrolase (EC 3.1.2.2) of rat liver microsomes have been studied. The hydrolase sedimented as a homogeneous species with a sedimentation coefficient, S20,W, of 4.1 S and the molecular weight of 59000 was obtained. Amino acid composition of the enzyme was determined. The specific absorption coefficient, A280nm1% was estimated as 9.8 (1 cm cell length) and the circular dichroic data suggested 50-60% alpha-helical structure. The enzyme contained three sulphydryl groups, and one of these was exposed to the environment. The hydrolase was inhibited by the serine-directed reagent phenylmethylsulfonyl fluoride, as well as p-hydroxymercuribenzoate, N-ethylmaleimide and 5,5'-dithiobis(2-nitrobenzoic acid). Reactivation by means of dithiothreitol was never complete with phenylmethylsulfonyl fluoride and p-hydroxymercuribenzoate as inhibitors.