title: Differences between microsomal and mitochondrial-matrix palmitoyl-coenzyme A hydrolase, and palmitoyl-L-carnitine hydrolase from rat liver.
abstract: Palmitoyl-CoA hydrolase (EC 3.1.2.2) and palmitoyl-L-carnitine hydrolase (EC 3.1.1.28) activities from rat liver were investigated. 1. Microsomal and mitochondrial-matrix palmitoyl-CoA hydrolase activities had similar pH and temperature optima, although the activities showed different temperature stability. They were inhibited by Pb2+ and Zn2+. The palmitoyl-CoA hydrolase activities in microsomal fraction and mitochondrial matrix were differently affected by the addition of Mg2+, Ca2+, Co2+, K+ and Na+ to the reaction mixture. ATP, ADP and NAD+ stimulated the microsomal activity and inhibited the mitochondrial-matrix enzyme. The activity of both the microsomal and mitochondrial-matrix hydrolase enzymes was specific for long-chain fatty acyl-CoA esters (C12-C18), with the highest activity for palmitoyl-CoA. The apparent Km for palmitoyl-CoA was 47 microM for the microsomal enzyme and 17 microM for the mitochondrial-matrix enzyme. 2. The palmitoyl-CoA hydrolase and palmitoyl-L-carnitine hydrolase activities of microsomal fraction had similar pH optima and were stimulated by dithiothreitol, but were affected differently by the addition of Pb2+, Mg2+, Ca2+, Mn2+ and cysteine. The two enzymes had different temperature-sensitivities. 3. The data strongly suggest that palmitoyl-CoA hydrolase and palmitoyl-L-carnitine hydrolase are separate microsomal enzymes, and that the hydrolysis of palmitoyl-CoA in the microsomal fraction and mitochondria matrix was catalysed by two different enzymes.
mesh_terms: D000818:Animals; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D006358:Hot Temperature; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology*; D008930:Mitochondria, Liver / Q000187:drug effects / Q000201:enzymology*; D009711:Nucleotides / Q000494:pharmacology; D010170:Palmitoyl-CoA Hydrolase / Q000378:metabolism*; D010172:Palmitoylcarnitine / Q000378:metabolism; D051381:Rats; D013379:Substrate Specificity; D013869:Thiolester Hydrolases / Q000378:metabolism*
chemical_list: D009711:Nucleotides; D010172:Palmitoylcarnitine; D002265:Carboxylic Ester Hydrolases; D013869:Thiolester Hydrolases; D010170:Palmitoyl-CoA Hydrolase