Specificity of two different purified acylcarnitine hydrolases from rat liver, their identity with other carboxylesterases, and their possible function

Arch Biochem Biophys. 1985 Aug 1;240(2):801-10. doi: 10.1016/0003-9861(85)90089-x.


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.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetylcarnitine / metabolism
  • Animals
  • Butyrylthiocholine / metabolism
  • Carboxylic Ester Hydrolases / metabolism*
  • Carnitine / metabolism
  • Hydrolysis
  • Isoelectric Point
  • Isoenzymes / metabolism*
  • Kinetics
  • Liver / enzymology*
  • Microsomes, Liver / enzymology
  • Palmitoyl Coenzyme A / metabolism
  • Rats


  • Isoenzymes
  • Palmitoyl Coenzyme A
  • Butyrylthiocholine
  • Acetylcarnitine
  • Carboxylic Ester Hydrolases
  • acylcarnitine hydrolase
  • Carnitine