A single amino acid substitution, Gly 117His, confers phosphotriesterase (organophosphorus acid anhydride hydrolase) activity on human butyrylcholinesterase

Oksana Lockridge, Renee M. Blong, Patrick Masson, Marie Thérèse Froment, Charles B. Millard, Clarence A. Broomfield

Research output: Contribution to journalArticle

141 Scopus citations

Abstract

The G117H mutant of human butyrylcholinesterase (EC 3.1.1.8) was expressed in Chinese hamster ovary cells. Substitution of Gly 117 with His to make the G117H mutant endowed butyrylcholinesterase with the ability to catalyze the hydrolysis of organophosphate esters. G117H was still able to hydrolyze butyrylthiocholine, benzoylcholine, and o-nitrophenyl butyrate, but in addition it had acquired the ability to hydrolyze the antiglaucoma drug echothiophate and the pesticide paraoxon. Wild-type butyrylcholinesterase was irreversibly inhibited by echothiophate and paraoxon, but G117H regained 100% activity within 2-3 min following reaction with these compounds. On a polyacrylamide gel, the same bands that stained for activity with butyrylthiocholine also stained for activity with echothiophate. G117H is the only enzyme known that hydrolyzes echothiophate. Diethoxyphosphorylated G117H aged with a half-time of 5.5 h, a rate 600 times slower than the rate of hydrolysis. Echothiophate and paraoxon were hydrolyzed with the same k(cat) of 0.75 min-1. This calculates to a rate acceleration of 100 000-fold for hydrolysis of echothiophate and paraoxon by the G117H mutant compared to the nonenzymatic rate.

Original languageEnglish (US)
Pages (from-to)786-795
Number of pages10
JournalBiochemistry
Volume36
Issue number4
DOIs
StatePublished - Jan 28 1997

ASJC Scopus subject areas

  • Biochemistry

Fingerprint Dive into the research topics of 'A single amino acid substitution, Gly 117His, confers phosphotriesterase (organophosphorus acid anhydride hydrolase) activity on human butyrylcholinesterase'. Together they form a unique fingerprint.

  • Cite this