Palmitoyl-coenzyme A hydrolyzing activity in rat kidney and its relationship to carboxylesterase

Palmitoyl-coenzyme A (palmitoyl-CoA) hydrolase was obtained from rat kidney in an electrophoretically homogeneous form. The enzyme associated with carboxylesterase activity was purified by acetone precipitation of microsomes, followed by successive chromatographies on DEAE-cellulose, phenyl-Sepharose, and Sephadex G-100 gel. The two activities in rat kidney were associated as judged by their co-elution profiles, co-purification at different steps, co-precipitation by an antibody raised against the purified enzyme, and identical profiles of inhibition by diisopropylfluorophosphate. The enzyme catalyzed the hydrolysis of long- and medium-chain acyl-CoA, but not short-chain acyl-CoA. The N-terminal amino acid sequence of the first 27 residues of the purified enzyme was 80% identical with that of the carboxylesterase from rat adipose tissue. Using a polyclonal rabbit antibody against the rat kidney palmitoyl-CoA hydrolase, the enzyme was demonstrated in liver but not in adipose tissue. The antibody reacted with the carboxylesterase(s) (pI 6.3 and pI 6.6) in rat liver microsomes. The antibody removed the palmitoyl-CoA hydrolase in kidney (75%) and liver (68%). The antibody also removed the monoolein hydrolase in kidney (77%) and liver (61%). These results suggest that carboxylesterase contributes to the hydrolysis of long-chain acyl-CoA and monoglyceride in kidney and liver.