Large differences in metabolic activation and inactivation of chemically closely related compounds: effects of pure enzymes and enzyme induction on the mutagenicity of the twelve monomethylated benz[a]anthracenes, 7,12-dimethylbenz[a]anthracene and benz[a]anthracenes in the Ames test

Epoxides derived from various polycyclic hydrocarbons as substrates of homogeneous and microsome-bound epoxide hydratase. A general assay and kinetic properties.

A general assay for epoxide hydratase using epoxides derived from polycyclic aromatic hydrocarbons as substrates is described. Addition of dimethylsulphoxide to the incubation mixture after incubation allowed unreacted epoxide and its phenolic by-product to be extracted into light petroleum whilst the product dihydrodiol remained in the aqueous phase. The product was then extracted into ethyl acetate and estimated radiochemically. This assay gave low extraction blanks (0.8-3.8%) when six K-region epoxides of polycyclic hydrocarbons were used, with high recoveries of the corresponding dihydrodiol in the ethyl acetate phase (65-89%). Radiochromatograms demonstrated that all the radioactivity …