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-hydro-xymethylpyrene (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. (c) 2007 Elsevier Inc. All rights reserved.
Gerasimenko,Yu.E.; Poteleshchenko,V.P., Journal of Organic Chemistry USSR (English Translation), 1972, vol. 8, p. 1084 - 1087
作者:Gerasimenko,Yu.E.、Poteleshchenko,V.P.
DOI:——
日期:——
Sorption of Polycyclic Aromatic Compounds to Humic Acid As Studied by High-Performance Liquid Chromatography
作者:Torben Nielsen、Katrin Siigur、Christian Helweg、Ole Jørgensen、Poul Erik Hansen、Uuve Kirso
DOI:10.1021/es960620t
日期:1997.4.1
Aldrich humic acid was chemically immobilized to the silanol surface of a column material to be used for highperformance liquid chromatography (HPLC). The retention factors to the humic acid column material of 45 polycyclic aromatics compounds (PAC) were determined by HPLC. The PAC include PAH, N-, S-, O-PAC and substituted PAC (9-substituted anthracenes, bromopyrenes, and quinoline derivatives). The sorption coefficient of quinoline to humic acid was directly determined at different pH. The good correlation achieved between the HPLC retention factors and literature K-oc values, including the presented one of quinoline, was applied to determine K-oc of 39 other PAC. The determined K-oc values were parametrized with regard to size, ring heteroatoms, and steric and substituent effects and were compared with literature values of water solubility and recently determined octanol-water partition coefficients. It is shown that the sorption of PAC to humic a cid is not only affected by hydrophobic interactions but also by hydrogen and especially ionic bonds. The investigation shows that the application of humic acid stationary HPLC phases is a valuable supplement to other techniques for determination of K-oc.