Effect of HD on the GD/GB Defluorinating Activity of the OPAA and OPH enzymes

摘要

The recombinant OPAA enzyme from Alteromonas sp. strain JD6.5, the recombinant OPH enzyme from Pseudomonas diminuta, and Flavobacterium sp. bacteria catalyze the hydrolysis of a number of toxic organophosphorus cholinesterase inhibiting compounds, including pesticides and chemical nerve agents. Because these enzymes are candidates for use in a catalytic chemical agent decontaminant, and might be relied on as decontaminants in an HD- contaminated environment, it is important to determine the effects of HD on enzyme activity. The GD activity of OPAA and the GB activity of OPH were measured in the presence of varying concentrations of HD pre-incubated with the enzyme. At low HD concentrations (up to 0.08 mg/mL), with a 1-min pre- incubation, OPAA activity on GD is stimulated up to 15%. The maximum stimulation occurs at 0.01 mg/mL HD. At higher HD concentrations, OPAA GD activity is gradually inhibited. The inhibition becomes asymptotic at about 70% of the native activity in the absence of HD (30% inhibition). An increase in HD-enzyme pre-incubation time gradually increases the inhibition of OPAA GD activity. However, even after 15 min of pre-incubation with a > 900,000-fold molar excess of HD (2500-fold gravimetric excess), almost 40% or the native activity remained. The inhibition of OPH GB activity was more pronounced than with OPAA; however, the enzyme still retained approximately 25% of its activity after a 1- min incubation of 0.32 micrograms/mL OPH with 6.5 mg/mL HD.