title: Efficient oxidation of promutagenic hydroxymethylpyrenes by cDNA-expressed human alcohol dehydrogenase ADH2 and its inhibition by various agents.
abstract: Alkylated polycyclic aromatic hydrocarbons can be metabolically activated via benzylic hydroxylation and sulphation to electrophilically reactive esters. However, we previously found that the predominant biotransformation route for the hepatocarcinogen 1-hydroxymethylpyrene (1-HMP) in the rat in vivo is the oxidation of the side chain by alcohol dehydrogenases (ADHs) and aldehyde dehydrogenases to the carboxylic acid. Inhibition of this pathway by ethanol (competing ADH substrate) or 4-methylpyrazole (ADH inhibitor) led to a dramatic increase in the 1-HMP-induced DNA adduct formation in rat tissues in the preceding study. In order to elucidate the role of individual ADHs in the metabolism of alkylated polycyclic aromatic hydrocarbons, we expressed the various members of the human ADH family in bacteria. Cytosolic preparations from bacteria expressing ADH2 clearly oxidized hydroxymethylpyrene isomers (1-, 2- and 4-HMP) with the highest rate. This form was purified to near homogeneity to perform detailed kinetic analyses. High catalytic efficiencies (V(max)/K(m)) were observed with HMPs. Thus, this value was 10,000-fold higher for 2-HMP than for the reference substrate, ethanol. The corresponding aldehydes were also efficiently reduced by ADH2. 4-Methylpyrazole inhibited the oxidation of the HMP isomers as well as the reverse reaction. Daidzein, cimetidine and the competing substrate ethanol were further compounds that inhibited the ADH2-mediated oxidative detoxification of 1-HMP.
authors.affiliation: German Institute of Human Nutrition Potsdam-Rehbruecke, Department of Nutritional Toxicology, 14558 Nuthetal, Germany.
authors.forename: Ronny
authors.initials: R
authors.lastname: Kollock
authors.forename: Walter
authors.initials: W
authors.lastname: Meinl
authors.forename: Heiko
authors.initials: H
authors.lastname: Schneider
authors.forename: Monika
authors.initials: M
authors.lastname: Batke
authors.forename: Heinz
authors.initials: H
authors.lastname: Frank
authors.forename: Albrecht
authors.initials: A
authors.lastname: Seidel
authors.forename: Hansruedi
authors.initials: H
authors.lastname: Glatt
mesh_terms: D000426:Alcohol Dehydrogenase / Q000037:antagonists & inhibitors / Q000235:genetics / Q000302:isolation & purification / Q000502:physiology*; D001711:Biotransformation; D002384:Catalysis; D003600:Cytosol / Q000378:metabolism; D000431:Ethanol / Q000009:adverse effects; D006801:Humans; D009153:Mutagens / Q000378:metabolism*; D010084:Oxidation-Reduction; D011721:Pyrenes / Q000378:metabolism*; D012907:Smoking / Q000009:adverse effects
chemical_list: D009153:Mutagens; D011721:Pyrenes; D000431:Ethanol; C065833:1-hydroxymethylpyrene; C489332:ADH1B protein, human; D000426:Alcohol Dehydrogenase