Abstract
Abstract 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 18-fold by diethylaminoethyl cellulose chromatography and Sephadex gel filtration. The purified enzyme sedimented in the ultracentrifuge as a single protein with an s20,w of 4.5 S. The enzyme had maximum activity at pH 7.5 and hydrolyzed higher fatty acid (C6 to C18) 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, p-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 10-3 m and for the palmitate ester 5 x 10-3 m. The enzyme was not affected by l-carnitine, dl-carnitine, d-carnitine, ethylenediaminetetraacetic acid, and Mg++ but it was inhibited by decanoyl-d-carnitine, Ca++, Cu++, NaF, sulfhydryl reagents, and sodium cholate, and it was activated by bovine serum albumin. The properties of carnitine ester hydrolase which distinguish it from microsomal esterase and microsomal lipase are discussed.
Highlights
SUMMARYKidney, pancreas, and small intestine have enzymes which hydrolyze fatty acid esters of carnitine
In the course of studies on the effect of other subcellular fractions on the oxidation of palmitoyl-L-carnitine by isolated rat liver mitochondria, it was observed that the microsomal fraction hydrolyzed the ester
The present paper describes the purification and properties of such an enzyme from rat liver
Summary
Kidney, pancreas, and small intestine have enzymes which hydrolyze fatty acid esters of carnitine. The enzyme had maximum activity at pH 7.5 and hydrolyzed higher fatty acid (C, to C,,) esters of L-carnitine. Esters of DL-carnitine were hydrolyzed only about one-half as efficiently as those of the. Among the L-carnitine esters, maximum rate of hydrolysis was obtained with the decanoate ester. In the course of studies on the effect of other subcellular fractions on the oxidation of palmitoyl-L-carnitine by isolated rat liver mitochondria, it was observed that the microsomal fraction hydrolyzed the ester. To the best of our knowledge, no enzyme catalyzing the hydrolysis of carnitine esters in animal tissues has been reported in the literature. The present paper describes the purification and properties of such an enzyme from rat liver
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