| The hydrolysis of Bis (p-nitrophenyl) phosphate (BNPP), an organophosphorous diester, by phosphodiesterase (PDE) and p-nitrophenylphosphate (PNPP), an organophosphorous monoester, by phosphomonoesterase (PME) was examined. The physiological as well as toxicological significance of these pathways were investigated in the earthworm Lumbricus terrestris. PME activity had two pH optima, indicating the presence of acid and alkaline phosphatases, and PDE activity had an alkaline pH optimum. Both enzyme appeared to be relatively stable at 40;The hydrolysis of BNPP and PNPP produced a final metabolite, p-nitrophenol, which was more toxic than BNPP and PNPP, suggesting that hydrolysis would be a bioactivation pathway. The results of an artificial soil test demonstrate that the toxicity of BNPP is enhanced by the presence of these hydrolases in the enteric cavity. |
