Hydroxymethylvinyl Ketone:  A Reactive Michael Acceptor Formed by the Oxidation of 3-Butene-1,2-diol by cDNA-Expressed Human Cytochrome P450s and Mouse, Rat, and Human Liver Microsomes

Abstract

The metabolic fate of 3-butene-1,2-diol (BDD), a secondary metabolite of the industrial carcinogen, 1,3-butadiene, is unclear. The current study characterizes BDD oxidation to hydroxymethylvinyl ketone (HMVK), a reactive Michael acceptor. Because of its instability in aqueous medium, HMVK was trapped by conjugation with GSH, a reaction that occurred readily at physiological conditions (pH 7.4, 37 degrees C) to yield 1-hydroxy-2-keto-4-(S-glutathionyl)butane. The results show that BDD was oxidized to HMVK by mouse, rat, and human liver microsomes and by cDNA-expressed human cytochrome P450s. Eadie-Hofstee plots demonstrated biphasic kinetics of BDD oxidation with mouse and rat liver microsomes and one of three individual human liver microsomes; BDD oxidation by the other two human liver microsomal samples was best described by monophasic kinetics. Of the human P450 enzymes examined, only P450 2E1 exhibited activity at 1 mM BDD. P450 3A4 was capable of catalyzing the reaction at a high BDD (10 mM) concentration; P450 1A1, 1A2, 1B1, 2D6-Met, and 2D6-Val produced only trace amounts of HMVK-GSH whereas P450 2A6, 2C8, 2C9, and 4A11 had no detectable activity. Detection of HMVK or the HMVK-GSH conjugate was dependent on reaction time, protein, and BDD concentrations, and the presence of NADPH. Collectively, the results provide clear evidence for BDD bioactivation to yield HMVK. Because mouse, rat, and human liver microsomes exhibited K(m) values of 50-80 microM, the results also suggest that HMVK could be formed after rodent or human exposure to BDD or its parent compound, BD.

Analysis of Diepoxide-Specific Cyclic N -Terminal Globin Adducts in Mice and Rats after Inhalation Exposure to 1,3-Butadiene

“…These phenomena are most likely due to the fact that 1,2,3-trihydroxybutyl-valine, as suggested previously, is mainly derived from the 3-butene-1,2-diol pathway (15)(16)(17). 3-Butene-1,2-diol, the precursor to 3,4-epoxy-1,2-butanediol, may also be converted to hydroxymethylvinyl ketone (18), that itself can form DNA (19) and N-terminal valine adducts (Dr. Mark Powley, personal communication). We are currently developing biomarker methods for the analysis of hydroxymethylvinyl ketonederived DNA and protein adducts, which in combination with 1,2,3-trihydroxybutyl adducts will allow estimating the portion of 1,2-epoxy-3-butene that is metabolized via the 3-butene-1,2-diol pathway.…”

A Comprehensive Listing of Bioactivation Pathways of Organic Functional Groups

“…The compound undergoes metabolism to several potential toxic intermediates; one of them is hydroxymethylvinyl ketone (HMVK), a Michael acceptor [418]. 1, 3-butadiene is initially metabolized to butadiene monoxide by P450 enzymes and myeloperoxidase (Fig.…”

Detection of Carboxylic Acids and Inhibition of Hippuric Acid Formation in Rats Treated With 3-Butene-1,2-Diol, a Major Metabolite of 1,3-Butadiene

“…Their low levels indicate that there may be competition for each step in the pathway. Our laboratory showed that the primary and secondary hydroxyl group of BDD can be selectively oxidized by ADH and P450s, respectively (Kemper and Elfarra, 1996;Krause et al, 2001). The oxidation of the secondary hydroxyl moiety of BDD results in the formation of hydroxymethylvinylketone, a Michael acceptor, and a very reactive compound.…”