Organophosphate inhibition of an arylesterase from Lumbricus terrestris and reversal by pralidoxime

Several enzymes of xenobiotic metabolism have been identified in soil annelids. Their roles in the physiology and ecotoxicology of the organism are diverse and may parallel those found in mammalian species. Among these are the arylesterases. An arylesterase assayed by hydrolysis of p-nitrophenylacetate was identified in Lumbricus terrestris. This arylesterase appears to be a serine esterase, since it is sensitive to inhibition by metrifonate. This mechanism of inhibition is similar to that of cholinesterase, since pralidoxime can reverse the inhibition of arylesterase by metrifonate. The presence of this esterase in soil annelids may provide insight into the processing of environmental chemicals by soil annelids as well as in vitro commercial applications of esterases based upon their mechanism of catalysis and inhibition.