PMID: 3753463Jun 1, 1986Paper

Kinetics of substrate hydrolysis and inhibition by mipafox of paraoxon-preinhibited hen brain esterase activity

The Biochemical Journal
C D Carrington, M B Abou-Donia

Abstract

For the purpose of assessing the neurotoxic potential of organophosphorus compounds, it has been determined that paraoxon-preinhibited hen brain has both neurotoxicant (mipafox)-sensitive (neurotoxic esterase; NTE) and -insensitive esterase components. Several experiments designed to investigate the kinetic parameters governing the reaction of these esterases with two substrates and one organophosphorus inhibitor are presented. First, kinetic parameters for the hydrolysis of phenyl valerate and phenyl phenylacetate were measured. At 37 degrees C, the Km values of NTE for phenyl valerate and phenyl phenylacetate were found to be about 1.4 X 10(-3) and 1.6 X 10(-4) M respectively. At 25 degrees C, the Km of NTE for phenyl valerate was determined to be about 2.4 X 10(-3) M. Secondly, the kinetic constants of NTE for mipafox were measured at both 25 degrees C and 37 degrees C. With either phenyl valerate or phenyl phenylacetate as substrate, the Km at 37 degrees C was determined to be about 1.8 X 10(-4) M, and the phosphorylation constant (k2) was about 1.1 min-1. For phenyl valerate only, the Km at 25 degrees C was found to be about 6 X 10(-4) M, and the k2 was about 0.7 min-1. The data obtained at 25 degrees C were analysed by us...Continue Reading

Citations

Jan 1, 1991·Critical Reviews in Toxicology·M Lotti
Mar 1, 1990·Toxicology and Applied Pharmacology·M K Johnson
Jun 1, 1993·Chemico-biological Interactions·E VilanovaV Carrera
Jan 1, 1988·Journal of Toxicology and Environmental Health·C D Carrington, M B Abou-Donia
Dec 15, 1990·Biochemical Pharmacology·T C ThomasM G McNamee

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