Carnitine ester hydrolase of rat liver.

Rat liver, kidney, pancreas, and small intestine have enzymes which hydrolyze fatty acid esters of carnitine. The liver enzyme, located in the microsomal fraction, was solubilized by sonic disruption and purified l&fold by diethylaminoethyl cellulose chromatography and Sephadex gel filtration. The purified enzyme sedimented in the ultracentrifuge as a single protein with an szo+, of 4.5 S. The enzyme had maximum activity at pH 7.5 and hydrolyzed higher fatty acid (C, to C,,) esters of L-carnitine. D-Carnitine esters were not hydrolyzed. Esters of DL-carnitine were hydrolyzed only about one-half as efficiently as those of the L isomer. The enzyme did not hydrolyze palmitoyl coenzyme A, @-nitrophenyl palmitate, glycerol tripalmitate, and cholesterol palmitate, but it catalyzed the hydrolysis of glycerol monopalmitate to a slight extent. Among the L-carnitine esters, maximum rate of hydrolysis was obtained with the decanoate ester. The Km for decanoate ester was 3.2 x 1OV M and for the palmitate ester 5 X 10e3 M. The enzyme was not affected by L-carnitine, DL-Carnitine, n-carnitine, ethylenediaminetetraacetic acid, and Mg+f but it was inhibited by decanoyl-D-carnitine, Ca++, Cu++, NaF sulfhydryl reagents, and sodium cholate, and it was activate; by bovine serum albumin. The properties of carnitine ester hydrolase which distinguish it from microsomal esterase and microsomal lipase are discussed.