Hydrolysis of paraoxon in mammalian blood.

Abstract

SEVERAL publications have indicated that in the detoxication of paraoxon (diethyl p-nitrophenyl phosphate, ‘E600,’ ‘Mintacol’) the mammalian blood serum might be of importance1–3. Aldridge4 was first to describe the existence of an A esterase (aryl-, aromatic esterase) which hydrolyses paraoxon. This enzyme occurs in the sera of various species1, but the extent of its involvement in the metabolism of paraoxon is not yet clear5,6. Among other properties, the arylesterase cleaves phenyl acetate7, and it has been shown with this substrate that the enzyme requires the presence of calcium for activity8,9. The arylesterase is activated by calcium and inhibited by sodium ethylenediaminetetraacetate and numerous other compounds8–11. In human blood plasma it occurs in fraction IV–112,13. Since preliminary experiments indicated that in addition to this arylesterase, at least one more factor might be responsible for the hydrolysis of paraoxon in blood serum or plasma, we undertook the present investigations.