Purification and cloning of a broad substrate specificity human liver carboxylesterase that catalyzes the hydrolysis of cocaine and heroin

Academic Article


  • A human liver carboxylesterase (hCE-2) that catalyzes the hydrolysis of the benzoyl group of cocaine and the acetyl groups of 4-methylumbelliferyl acetate, heroin, and 6-monoaeetylmorphine was purified from human liver. The purified enzyme exhibited a single band on SDS-polyacrylamide gel electrophoresis with a subunit mass of approximately 60 kDa. The native enzyme was monomeric. The isoelectric point of hCE-2 was approximately 4.9. Treatment with endoglycosidase H caused an increase in electrophoretic mobility indicating that the liver carboxylesterase was a glycoprotein of the high mannose type. The complete cDNA nucleotide sequence was determined. The authenticity of the cDNA was confirmed by a perfect sequence match of 78 amino acids derived from the hCE-2 purified from human liver. The mature 533- amine acid enzyme encoded by this cDNA shared highest sequence identity with the rabbit liver carboxylesterase form 2 (73%) and the hamster liver carboxylesterase AT51p (67%). Carboxylesterases with high sequence identity to hCE-2 have not been reported in mouse and rat liver. hCE-2 exhibited different drug ester substrate specificity from the human liver carboxylesterase called hCE-1, which hydrolyzes the methyl ester of cocaine. hCE-2 had higher catalytic efficiencies for hydrolysis of 4- methylumbelliferyl acetate, heroin, and 6-monoacetylmorphine and greater inhibition by eserine than hCE-1. hCE-2 may play an important role in the degradation of cocaine and heroin in human tissues.
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    Author List

  • Pindel EV; Kedishvili NY; Abraham TL; Brzezinski MR; Zhang J; Dean RA; Bosron WF
  • Start Page

  • 14769
  • End Page

  • 14775
  • Volume

  • 272
  • Issue

  • 23