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Updated: Aug 18, 2026

Defining Substrate Specificities for Lipase and Phospholipase Candidates
Published on: November 23, 2016
The kinetics of O-hexyl O-2,5-dichlorophenyl phosphoramidate hydrolysing activity in hen plasma
M A Sogorb1, E Vilanova, N Díaz-Alejo
1Department of Neurochemistry, University of Alicante, Spain.
Abstract:
The organophosphorus (OP) compound O-hexyl-O-2,5-dichlorophenyl phosphoramidate (H-DCP) is hydrolysed in the plasma, liver and brain of hens and rats. We study in hen plasma the effect of tissue and substrate concentrations and of pH on the hydrolysing activity of H-DCP. The data on each tissue concentration were fitted to a double exponential mathematical model. The kinetics of this activity was not linear; in a first exponential component or fast initial phase (k1 = (1.603 +/- 0.248) x 10(-3) min-1/microliter plasma (n = 4, S.E.)) about 15% of the total compound was hydrolysed, followed by a slow second phase (k2 = (0.144 +/- 0.026) x 10(-3) min-1/microliter plasma (n = 4, S.E.)) in which the remaining 85% was hydrolysed. Both constants increased in value with pH. The hydrolytic activity and rate constants increased with the amount of plasma, but no change in kinetics was observed. The kinetic data are discussed in terms to lend support to the hypothesis of a stereospecific degradation of H-DCP.
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