| 3999477 |
Sugiyama S, Igarashi T, Ueno K, Satoh T, Kitagawa H: NAD-coupled enzymatic oxidation of O-ethyl O-p-nitrophenyl phenylphosphonothioate (EPN) to its oxygen analog with liver microsomes of rats. Jpn J Pharmacol. 1985 Mar;37(3):245-52.
O-Ethyl O-p-nitrophenyl phenylphosphonothioate (EPN)-induced inhibition of rat liver microsomal carboxylesterase (CEase) and formation of O-ethyl O-p-nitrophenyl phenylphosphonate (EPNoxon), an oxygen analog of EPN, were enhanced remarkably by addition of NAD in vitro. This potentiation of the anti-CEase action of EPN by NAD was significantly inhibited by addition of SKF 525-A or potassium thiocyanate (KSCN); and a simultaneous decrease in cytochrome P-450 contents were also observed. Addition of N-ethylmaleimide (NEM) at various concentrations inhibited potentiation of the anti-CEase action of EPN by NAD in parallel with inhibition of liver microsomal dehydrogenase activities. In conclusion, NAD was enzymatically reduced to NADH, a cofactor of microsomal dehydrogenase (s), and then formation of EPNoxon through microsomal cytochrome P-450-coupled monooxygenase was accelerated. Consequently, inhibition of CEase by EPN was potentiated. |
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