title: Dehydroalanine analog of glutathione: an electrophilic busulfan metabolite that binds to human glutathione S-transferase A1-1.
abstract: Elimination of hydrogen sulfide from glutathione (GSH) converts a well known cellular nucleophile to an electrophilic species, gamma-glutamyldehydroalanylglycine (EdAG). We have found that a sulfonium metabolite formed from GSH and busulfan undergoes a facile beta-elimination reaction to give EdAG, which is an alpha,beta-unsaturated dehydroalanyl analog of GSH. EdAG was identified as a metabolite of busulfan in a human liver cytosol fraction. EdAG condenses with GSH in a Michael addition reaction to produce a lanthionine thioether [(2-amino-5-[[3-[2-[[4-amino-5-hydroxy-5-oxopentanoyl]amino]-3-(carboxymethylamino)-3-oxopropyl]sulfanyl-1-(carboxymethylamino)-1-oxopropan-2-yl]amino]-5-oxopentanoic acid); GSG], which is a nonreducible analog of glutathione disulfide. EdAG was less cytotoxic than busulfan to C6 rat glioma cells. GSH and EdAG were equally effective in displacing a glutathione S-transferase (GST) isozyme (human GSTA1-1) from a GSH-agarose column. The finding of an electrophilic metabolite of GSH suggests that alteration of cellular GSH concentrations, irreversible nonreducible glutathionylation of proteins, and interference with GST function may contribute to the toxicity of busulfan.
authors.affiliation: Department of Basic Pharmaceutical Sciences, West Virginia University, Morgantown, WV 26506, USA.
authors.forename: Islam R
authors.initials: IR
authors.lastname: Younis
authors.forename: Meenal
authors.initials: M
authors.lastname: Elliott
authors.forename: Cody J
authors.initials: CJ
authors.lastname: Peer
authors.forename: Arthur J L
authors.initials: AJ
authors.lastname: Cooper
authors.forename: John T
authors.initials: JT
authors.lastname: Pinto
authors.forename: Gregory W
authors.initials: GW
authors.lastname: Konat
authors.forename: Michal
authors.initials: M
authors.lastname: Kraszpulski
authors.forename: William P
authors.initials: WP
authors.lastname: Petros
authors.forename: Patrick S
authors.initials: PS
authors.lastname: Callery
mesh_terms: D000409:Alanine / Q000031:analogs & derivatives; D000818:Animals; D018906:Antineoplastic Agents, Alkylating; D002066:Busulfan / Q000378:metabolism* / Q000494:pharmacology; D045744:Cell Line, Tumor; D005910:Glioma / Q000188:drug therapy; D005978:Glutathione / Q000031:analogs & derivatives* / Q000378:metabolism*; D019803:Glutathione Disulfide / Q000031:analogs & derivatives; D005982:Glutathione Transferase / Q000378:metabolism*; D006801:Humans; D008099:Liver; D051381:Rats
chemical_list: D018906:Antineoplastic Agents, Alkylating; C000603515:gamma-glutamyl-dehydroalanyl-glycine; C015102:dehydroalanine; C484555:GSTA1 protein, human; D005982:Glutathione Transferase; D002066:Busulfan; D005978:Glutathione; D000409:Alanine; D019803:Glutathione Disulfide
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