title: Examination of diols and diol epoxides of polycyclic aromatic hydrocarbons as substrates for rat liver dihydrodiol dehydrogenase.
abstract: Dihydrodiol dehydrogenase (DD; EC 1.3.1.20) can suppress the formation of anti-diol epoxides that arise from the metabolic activation of PAH by oxidizing their precursor trans-dihydrodiols to o-quinones [Smithgall, T.E., et al. (1988) J. Biol. Chem. 263, 1814-1820]. DD has also been found to reduce the mutagenicity of benz[a]anthracene (+/-)-anti-8,9-dihydrodiol 10,11-epoxide [(+/-)-anti-BADE] in the Ames test (Glatt, H.R., et al. (1982) Science 215, 1507-1509), suggesting that anti-diol epoxides are substrates for this enzyme. In this study, attempts have been made to demonstrate directly that diol epoxides of PAH are substrates for homogeneous DD. Spectrophotometric assays indicate that high concentrations of the stable anti-diol epoxides, naphthalene (+/-)-anti-1,2-dihydrodiol 3,4-epoxide (10 mM) and (+/-)-anti-BADE (20 microM; limit of solubility) were not oxidized by micromolar concentrations of enzyme. By contrast, 20 microM (+/-)-trans-7,8-dihydroxy-7,8-dihydrobenzo[a]pyrene [(+/-)-trans-BP-diol] was oxidized by 50-fold less enzyme. Using a reverse-phase high-performance liquid chromatography (RP-HPLC)-based assay [1,3-3H]-(+/-)-trans-BP-diol could be almost completely oxidized by DD in the presence of NADP+. Using a similar assay, [1,3-3H]benzo[a]pyrene (+/-)-anti-7,8-dihydrodiol 9,10-epoxide [(+/-)-anti-BPDE], and unlabeled (+/-)-syn-BPDE and (+/-)-anti-BADE were tested as substrates for DD.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacology, University of Pennsylvania School of Medicine, Philadelphia 19104.
authors.forename: L
authors.initials: L
authors.lastname: Flowers-Geary
authors.forename: R G
authors.initials: RG
authors.lastname: Harvey
authors.forename: T M
authors.initials: TM
authors.lastname: Penning
mesh_terms: D000429:Alcohol Oxidoreductases / Q000378:metabolism*; D000818:Animals; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000201:enzymology; D004852:Epoxy Compounds / Q000378:metabolism; D066298:In Vitro Techniques; D008099:Liver / Q000201:enzymology*; D010088:Oxidoreductases; D044925:Oxidoreductases Acting on CH-CH Group Donors; D011083:Polycyclic Compounds / Q000378:metabolism*; D051381:Rats; D013053:Spectrophotometry
chemical_list: D004852:Epoxy Compounds; D011083:Polycyclic Compounds; D010088:Oxidoreductases; D000429:Alcohol Oxidoreductases; C023125:dihydrodiol dehydrogenases; D044925:Oxidoreductases Acting on CH-CH Group Donors; C116788:cis-1,2-dihydro-1,2-dihydroxynaphthalene dehydrogenase