O. Lockridge, D. M. Quinn

Research output: Chapter in Book/Report/Conference proceedingChapter

21 Scopus citations


Human plasma contains two esterases: butyrylcholinesterase and paraoxonase. In contrast to rodents, human plasma contains no carboxylesterase. Human red blood cells contain glycolipid-anchored acetylcholinesterase outside and esterase D inside the cells. The esterase activity of albumin is a half-reaction in which lysines are acylated by esters without turnover. Paraoxonase 1 (PON1) is part of the high-density lipoprotein complex. Liver, lung, intestine, and other tissues contain a total of 31 esterases including four carboxylesterases, two paraoxonases, fourteen thioesterases, six lipases, two cholinesterases, one methylesterase, one platelet-activating factor acetylhydrolase, and one sialate O-acetylesterase. Esterases detoxicate cocaine, organophosphorus pesticides, pyrethroid insecticides, nerve agents, succinylcholine, mivacurium, ritalin, aspirin, esmolol, and demerol. The prodrugs irinotecan, bambuterol, Tamiflu, trandolapril, imidapril, temocapril, and ciclesonide are converted into active drugs by esterases. Genetic variants of human butyrylcholinesterase, carboxylesterase, paraoxonase, and esterase D affect the metabolism of ester drugs. A mutation in human acetylcholinesterase that changes His322 to Asn has no effect on catalytic activity but does provide an epitope for antibody reactivity, making red blood cell acetylcholinesterase the YT2 blood group. Butyrylcholinesterase, acetylcholinesterase, carboxylesterase, and esterase D are characterized by a catalytic triad Ser-His-Glu (or Asp). Organophosphorus esters make a stable covalent bond with the active site serine, resulting in inhibition. The acute toxicity of organophosphorus pesticides and nerve agents is due to inhibition of acetylcholinesterase. The serine esterases have similar three-dimensional (3-D) alpha/beta hydrolase fold protein structures. Paraoxonase has a six-bladed beta propeller structure with two calcium ions in the active site cavity.

Original languageEnglish (US)
Title of host publicationBiotransformation
PublisherElsevier Inc.
Number of pages31
ISBN (Print)9780080468686
StatePublished - Aug 12 2010


  • Acetylcholinesterase
  • Butyrylthiocholine
  • Carboxylesterase
  • Esterase D
  • Nerve agents
  • Organophosphorus pesticides
  • Paraoxonase

ASJC Scopus subject areas

  • General Medicine


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