Isozyme-Selective Metabolism of Ethyl Carbamate by Cytochrome P450 (CYP2E1) and Carboxylesterase (Hydrolase A) Enzymes in Murine Liver Microsomes

摘要: Cytochrome P450 and carboxylesterase enzymes have been implicated in the metabolism of carcinogen ethyl carbamate (EC). In this study, we used a murine liver microsomal system to investigate relative contributions isozymes hepatic EC. N-Nitrosodimethylamine (NDMA) demethylation p-nitrophenyl acetate (PNA) hydrolysis were as catalytic markers CYP2E1 enzymes, respectively. Incubation microsomes with EC (1 mM) produced slight but significant decreases NDMA PNA activities. paraoxon (PAX), general inhibitor, or phenylmethylsulfonyl fluoride (PMSF), specific inhibitor hydrolase A, 85 45%, respectively, activities; neither inhibitors elicited alterations levels demethylation. Reaction either PAX PMSF then exacerbated reduction (285%) demethylation, loss corresponded immunodetectable content. The activity induced by PAX, PMSF, correlated decreased A microsomes; however, reaction not resulted immunoreactivity for B. These data covalent binding [ethyl-14C]EC microsomes, which significantly elevated incubations conducted PMSF. Antibody inhibition enzyme reduced proteins, compared control levels. results are consistent premise that is metabolized mice.