Use of monoclonal and polyclonal antibodies as structural and topographical probes for hepatic epoxide hydrolase

AbstractMonoclonal antibodies have been prepared against rat liver epoxide hydrolase (EH), some of which gave precipitation lines on immunodiffusion against pure EH suggesting the presence of repetitive structural domains on the enzyme. Using ELISA, with polyclonal antibodies to rat and rabbit liver EH, reactivity and therefore structural similarities between EH of all species tested, including human, were observed. This was in contrast to immunodiffusion results demonstrating the limitations of the latter technique. Using monoclonal antibodies in ELISA, greatest structural similarity was between rat, mouse, and Syrian hamster EH and relatively little between rat and human. Two of the antib…

Effects of the modulation of epoxide hydrolase activity on the binding of benzo[a]pyrene metabolites to DNA in the intact nuclei.

Metabolic activation and inactivation of chemical mutagens and carcinogens

Studies on the Biosynthesis of Microsomal Membrane Proteins. Site of Synthesis and Mode of Insertion of Cytochrome b5, Cytochrome b5 Reductase, Cytochrome P-450 Reductase and Epoxide Hydrolase

The site of synthesis and mechanism of insertion into membranes of several microsomal polypeptides was studied using translation system programmed in vitro with polysomes or with mRNA extracted from free and membrane-bound rat liver polysomes. Primary translation products of cytochrome b5, NADH: cytochrome b5 oxidoreductase, NADPH: cytochrome P-450 oxidoreductase and epoxide hydrolase were isolated by specific immunoprecipitation and compared with the mature proteins. The following observations were made: 1 While cytochrome b5 and NADH: cytochrome b5 oxidoreductase are synthesized in free polysomes, NADPH: cytochrome P-450 oxidoreductase and epoxide hydrolase are made in membrane-bound poly…

NADPH-cytochrome P-450 reductase: Preferential inhibition by ellipticine and other type II compounds having little effect on NADPH-cytochrome c reductase

Abstract Ellipticine (5,11-dimethyl-[6H]-pyrido[4,3b]carbazole) binds with an affinity greater than most other compounds known to interact with P-450. Control and 3-methylcholanthrene-induced aryl hydrocarbon (benzo[ a ]pyrene) hydroxylase (EC 1.14.14.2) and acetanilide 4-hydroxylase and control and phenobarbital-induced ethylmorphine N -demethylase activities are all markedly inhibited by ellipticine to about the same extent. Ellipticine and other Type II compounds (metyrapone, octylamine-1, pyridine and aniline) preferentially inhibit NADPH-cytochrome P-450 reductase activity, while affecting NADPH-cytochrome c reductase activity very little. Butanol-1, a compound having pure Reverse Type…

Modulation of Epdxide Hydrolase Activity; Effect on the Activation of Benzo Cal Pyrene and Its Covalent Binding to Dna in the Nucleus

Benzo[a]pyrene (BP), a model polycyclic aromatic hydrocarbon mutagen and carcinogen, requires bioactivation for the expression of its carcinogenic and mutagenic properties. This process occurs in multiple steps, the initial step being a conversion of BP to epoxide(s) by membrane-bound monooxygenases. The subsequent disposition of these electrophilic species can be directed towards toxic or nontoxic endpoints, depending upon the relative preponderance of several enzymatic and nonenzymatic processes within the cell. Epoxides formed from BP can rearrange to form phenols, be conjugated to glutathione, be converted by epoxide hydrolase to dihydrodiols or bind to cellular macromolecules (Jerina a…