title: Metabolism of trans,trans-muconaldehyde by aldehyde and alcohol dehydrogenases: identification of a novel metabolite.
abstract: The metabolism of trans,trans-muconaldehyde (MA), a highly reactive alpha,beta-unsaturated dialdehyde, was examined in vitro using purified yeast alcohol and aldehyde dehydrogenases (ADH and ALDH, respectively). In the presence of NAD(+)-fortified ALDH, the mono-oxidation product (acid/aldehyde) was the primary metabolite formed with trace amounts of the dioxidation product (trans,trans-muconic acid). In NADH-fortified reactions with ADH, both the mono- and direduction products (hydroxy/aldehyde and dihydroxy, respectively) were readily detected. Oxidation and reduction products of MA were formed in incubates containing both dehydrogenases together with either NAD+ or NADH. Unexpectedly, an additional metabolite was detected, which was a major product in both NAD(+)- and NADH-fortified systems containing ALDH and ADH in combination and whose formation could be inhibited by pyrazole (an ADH inhibitor). ALDH-mediated oxidation of a synthetic standard of the hydroxy/aldehyde derivative of MA resulted in formation of this new metabolite, which was also a major product formed by rat hepatocytes incubated with MA. Using HPLC/photodiode array detection, the new metabolite was found to cochromatograph and have a uv spectrum identical to that of a synthetic standard of the hydroxy/acid derivative of MA. The metabolite was confirmed as the hydroxy/acid derivative of MA after preparative HPLC, TMS derivatization, and GC/MS analysis. The hydroxy/acid metabolite was not formed during ADH-mediated reduction of the mono-oxidation product of MA, suggesting that this metabolite was formed by yeast dehydrogenases via a primary reduction of MA and subsequent oxidation of the hydroxy/aldehyde to the hydroxy/acid. These data show that the hydroxy/acid derivative is a novel metabolite of MA, which arises from the interaction of both oxidative and reductive routes of metabolism.
authors.affiliation: Molecular Toxicology and Environmental Health Sciences Program, School of Pharmacy, University of Colorado, Boulder 80309-0297.
authors.forename: D
authors.initials: D
authors.lastname: Goon
authors.forename: X
authors.initials: X
authors.lastname: Cheng
authors.forename: J A
authors.initials: JA
authors.lastname: Ruth
authors.forename: D R
authors.initials: DR
authors.lastname: Petersen
authors.forename: D
authors.initials: D
authors.lastname: Ross
mesh_terms: D000426:Alcohol Dehydrogenase / Q000378:metabolism*; D000444:Aldehyde Dehydrogenase / Q000378:metabolism*; D000447:Aldehydes / Q000378:metabolism*; D000818:Animals; D002478:Cells, Cultured / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D008297:Male; D008954:Models, Biological; D009243:NAD / Q000494:pharmacology; D010084:Oxidation-Reduction; D051381:Rats; D011919:Rats, Inbred Strains; D013237:Stereoisomerism
chemical_list: D000447:Aldehydes; D009243:NAD; C034476:muconaldehyde; D000426:Alcohol Dehydrogenase; D000444:Aldehyde Dehydrogenase