S-(2-Hydroxy-3-buten-1-yl)glutathione and S-(1-hydroxy-3-buten-2-yl)glutathione are in vivo metabolites of butadiene monoxide: detection and quantitation in bile

Self Cite

3-Butene-1,2-diol (BDD) is a metabolite of the carcinogenic petrochemical 1,3-butadiene. BDD is produced by cytochrome P450-mediated oxidation of 1,3-butadiene to butadiene monoxide, followed by enzymatic hydrolysis by epoxide hydrolase. The metabolic disposition of BDD is unknown. The current work characterizes BDD oxidation by purified horse liver alcohol dehydrogenase (ADH) and by cytosolic ADH from mouse, rat, and human liver. BDD is oxidized by purified horse liver ADH in a stereoselective manner, with (S)-BDD oxidized at approximately 7 times the rate of (R)-BDD. Attempts to detect and identify metabolites of BDD using purified horse liver ADH demonstrated formation of a single stable metabolite, 1-hydroxy-2-butanone (HBO). A second possible metabolite, 1-hydroxy-3-butene-2-one (HBONE), was tentatively identified by GC/MS, but HBONE formation could not be clearly attributed to BDD oxidation, possibly due to its rapid decomposition in the incubation mixture. Formation of HBO by ADH was dependent upon reaction time, protein concentration, substrate concentration, and the presence of NAD. Inclusion of GSH or 4-methylpyrazole in the incubation mixture resulted in inhibition of HBO formation. Based on these results and other lines of evidence, a mechanism is proposed for HBO formation involving generation of several potentially reactive intermediates which could contribute to toxicity of 1,3-butadiene in exposed individuals. Comparison of kinetics of BDD oxidation in rat, mouse, and human liver cytosol did not reveal significant differences in catalytic efficiency (Vmax/K(m)) between species. These results may contribute to a better understanding of 1,3-butadiene metabolism and toxicity.

Section: Introductionmentioning

confidence: 99%

Oxidation of 3-Butene-1,2-diol by Alcohol Dehydrogenase

Kemper

Elfarra

1996

Self Cite

“…Occupational exposure to 1,3-butadiene, a petrochemical used extensively in the industrial production of rubbers and plastics, has been implicated in the development of human cancer (1)(2)(3). In vivo and in vitro studies in rats and mice have suggested that 1,3-butadiene metabolism to yield the mutagenic and carcinogenic metabolites butadiene monoxide (BM1, Figure 1) and crotonaldehyde (CA) plays an important role in the mechanism(s) of 1,3butadiene-induced toxicity (4)(5)(6)(7)(8)(9)(10)(11)(12)(13). Studies conducted in our laboratory have also shown that, in addition to cytochrome P450s, enzymes such as myeloperoxidase and chloroperoxidase, a nonmammalian enzyme which appears to have a cytochrome P450-like active site (14)(15)(16)(17)(18), are capable of catalyzing 1,3-butadiene oxidation to BM and CA (5)(6)(7)(8)(9).…”

Section: Introductionmentioning

confidence: 99%

Chloroperoxidase-mediated oxidation of 1,3-butadiene to 3-butenal, a crotonaldehyde precursor

Duescher

Elfarra²

1993

Self Cite

Previously, we have shown that 1,3-butadiene, a rodent and possibly a human carcinogen, can be oxidized by chloroperoxidase-H2O2 at pH 7.4 to yield the potent mutagens, butadiene monoxide and crotonaldehyde. Because the crotonaldehyde/butadiene monoxide ratio from reactions with chloroperoxidase was higher than that obtained from reactions with myeloperoxidase or cytochrome P450 enzymes, in the present study, the chloroperoxidase reaction was further investigated in an attempt to define optimal conditions for catalysis and to possibly obtain direct evidence for the formation of the crotonaldehyde precursor 3-butenal in these incubations. The results showed that butadiene monoxide and crotonaldehyde formation was optimal at pH 6.0. As opposed to incubations carried out at pH 7.4, GC analyses of incubations carried out at pH 4.5, 5.0, and 6.0 demonstrated the presence of a new peak which had a retention time different from that of butadiene monoxide and crotonaldehyde. The new peak was identified as 3-butenal by comparison of its retention time and mass spectrum with those of reference material. Evidence for 3-butenal being a precursor of crotonaldehyde was obtained by the findings that 3-butenal was not simply a decomposition product of butadiene monoxide or crotonaldehyde under the incubation or assay conditions, and that the 3-butenal/crotonaldehyde ratio decreased when the incubation time was increased between 5 and 30 min or when the incubation temperature was increased between 10 and 45 degrees C. The combined 3-butenal and crotonaldehyde concentrations remained constant at the various incubation temperatures. Furthermore, 3-butenal conversion to crotonaldehyde was faster at pH 7.4, compared to pH 6.0.(ABSTRACT TRUNCATED AT 250 WORDS)

“…Because these studies suggest that BM may play a role in 1,3-butadiene-induced carcinogenicity, the metabolism and disposition of BM was investigated. In previous studies (16)(17)(18), we have shown that cytosolic glutathione S-transferase catalyzed the conjugation reaction of BM with glutathione (GSH) (Figure 1) in vitro to form S-(2-hydroxy-3-buten-l-yl)glutathione (BM-GSH I) and S-(l-hydroxy-3-buten-2-yl)glutathione (BM-GSH II). Pu-rified human placental glutathione S-transferase catalyzed the reaction with a Vmax of 500 nmol/(mg*min), and mouse liver, lung, kidney, and testis cytosolic fractions were also shown to catalyze the reaction at rates equal The three consecutive arrows represent metabolism of the GSH conjugate by y-glutamyl transpeptidase, followed by dipeptidase, and then acetylation by V-acetyltransferase.…”

mentioning

confidence: 98%

Synthesis and Characterization of N-Acetyl-L-cysteine S-Conjugates of Butadiene Monoxide and Their Detection and Quantitation in Urine of Rats and Mice Given Butadiene Monoxide

Elfarra¹,

Sharer²,

Duescher³

1995

Self Cite

Butadiene monoxide (BM), a mutagen and carcinogen, is the major metabolite of 1,3-butadiene in rats and mice. Because mercapturic acids (N-acetyl-L-cysteine S-conjugates) were expected in vivo metabolites of BM, reference BM-mercapturic acids were prepared by the reaction of racemic BM with N-acetyl-L-cysteine. Four isomers were purified and characterized as diastereomeric pairs of S-(2-hydroxy-3-buten-1-yl)-N-acetyl-L-cysteine (I) and S-(1-hydroxy-3-buten-2-yl)-N-acetyl-L-cysteine (II) based on analyses by 1H NMR, fast atom bombardment mass spectrometry, and high resolution electron impact mass spectrometry. Regioisomers I and II were identified in the urine of rats and mice administered (ip) BM based on GC/MS analyses performed after HPLC fractionation followed by esterification and silylation of the carboxyl and hydroxyl groups, respectively, and comparison of GC retention times with synthetic standards. S-(4-Hydroxy-2-buten-1-yl)-N-acetyl-L-cysteine, a rearrangement product formed during chemical synthesis or storage of both I and II under acidic conditions, was not detected; no other BM metabolites were evident in urine samples using this method. When rats were given BM at a dose of 71.5 to 285 mumol/kg, their urinary excretion of I and II within 8 h of BM administration exhibited linear relationships with the administered BM dose; the total amount of the BM dose excreted as combined I and II averaged 17 +/- 4% (mean +/- SD, n = 15). No metabolites were detected in urine samples collected between 8 and 24 h after BM dosing.(ABSTRACT TRUNCATED AT 250 WORDS)