title: Specificity of two different purified acylcarnitine hydrolases from rat liver, their identity with other carboxylesterases, and their possible function.
abstract: One of the previously described five purified monoglyceride-cleaving carboxylesterases from rat liver microsomes proved to be a carnitine ester hydrolase. This esterase, with an isoelectric point of 5.2, is most active with medium-chain acyl-L-carnitines (C12-C14). The esterase is also remarkably active with 1,3-diglycerides, especially 1,3-dioctanoylglycerol, that are hydrolyzed faster than the corresponding 1-monoglycerides and triglycerides. Only one of the other four purified carboxylesterases has moderate acylcarnitine-hydrolyzing activity. An altered procedure for the separation of the two microsomal acylcarnitine-cleaving enzymes is described. Both enzymes hydrolyze carnitine esters optimally at pH 8 and both are inactive with acetylcarnitine, palmitoyl-CoA, and butyrylthiocholine. The possible natural functions of the hydrolases are discussed. Besides their detoxifying action on natural membrane-lysing detergents (like carnitine esters and lysophospholipids), these enzymes could be involved in the transport of carnitine out of the liver.
mesh_terms: D000108:Acetylcarnitine / Q000378:metabolism; D000818:Animals; D002092:Butyrylthiocholine / Q000378:metabolism; D002265:Carboxylic Ester Hydrolases / Q000378:metabolism*; D002331:Carnitine / Q000378:metabolism; D006868:Hydrolysis; D007526:Isoelectric Point; D007527:Isoenzymes / Q000378:metabolism*; D007700:Kinetics; D008099:Liver / Q000201:enzymology*; D008862:Microsomes, Liver / Q000201:enzymology; D010171:Palmitoyl Coenzyme A / Q000378:metabolism; D051381:Rats
chemical_list: D007527:Isoenzymes; D010171:Palmitoyl Coenzyme A; D002092:Butyrylthiocholine; D000108:Acetylcarnitine; D002265:Carboxylic Ester Hydrolases; C019843:acylcarnitine hydrolase; D002331:Carnitine