title: Mass Spectrometric Characterization of Human Serum Albumin Adducts Formed with N-Oxidized Metabolites of 2-Amino-1-methylphenylimidazo[4,5-b]pyridine in Human Plasma and Hepatocytes.
abstract: 2-Amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), a carcinogenic heterocyclic aromatic amine formed in cooked meats, is metabolically activated to electrophilic intermediates that form covalent adducts with DNA and protein. We previously identified an adduct of PhIP formed at the Cys(34) residue of human serum albumin following reaction of albumin with the genotoxic metabolite 2-hydroxyamino-1-methyl-6-phenylimidazo[4,5-b]pyridine (HONH-PhIP). The major adducted peptide recovered from a tryptic/chymotryptic digest was identified as the missed-cleavage peptide LQQC*([SO2PhIP])PFEDHVK, a [cysteine-S-yl-PhIP]-S-dioxide linked adduct. In this investigation, we have characterized the albumin adduction products of N-sulfooxy-2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-sulfooxy-PhIP), which is thought to be a major genotoxic metabolite of PhIP formed in vivo. Targeted and data-dependent scanning methods showed that N-sulfooxy-PhIP adducted to the Cys(34) of albumin in human plasma to form LQQC*([SO2PhIP])PFEDHVK at levels that were 8-10-fold greater than the adduct levels formed with N-(acetyloxy)-2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (N-acetoxy-PhIP) or HONH-PhIP. We also discovered that N-sulfooxy-PhIP forms an adduct at the sole tryptophan (Trp(214)) residue of albumin in the sequence AW*([PhIP])AVAR. However, stable adducts of PhIP with albumin were not detected in human hepatocytes. Instead, PhIP and 2-amino-1-methyl-6-(5-hydroxy)phenylimidazo[4,5-b]pyridine (5-HO-PhIP), a solvolysis product of the proposed nitrenium ion of PhIP, were recovered during the proteolysis, suggesting a labile sulfenamide linkage had formed between an N-oxidized intermediate of PhIP and Cys(34) of albumin. A stable adduct was formed at the Tyr(411) residue of albumin in hepatocytes and identified as a deaminated product of PhIP, Y(*[desaminoPhIP])TK, where the 4-HO-tyrosine group bound to the C-2 imidazole atom of PhIP.
authors: †Masonic Cancer Center and Department of Medicinal Chemistry, Cancer and Cardiology Research Building, University of Minnesota, 2231 6th Street, Minneapolis, Minnesota 55455, United States.
authors: Yi
authors: Y
authors: Wang
authors: ‡School of Chemical and Environmental Engineering, Wuhan Polytechnic University, ChangQing Garden, Hankou, Wuhan 430023, P. R. China.
authors: Lijuan
authors: L
authors: Peng
authors: §Institut National de la Santé et de la Recherche Médicale (Inserm), U.1085, Institut de Recherche Santé Environnement et Travail (IRSET), Université de Rennes 1, UMS 3480 Biosit, F-35043 Rennes, France.|∥ANSES Laboratoire de Fougères, La Haute Marche-Javené, BP 90203, 350302 Fougères, France.
authors: Medjda
authors: M
authors: Bellamri
authors: §Institut National de la Santé et de la Recherche Médicale (Inserm), U.1085, Institut de Recherche Santé Environnement et Travail (IRSET), Université de Rennes 1, UMS 3480 Biosit, F-35043 Rennes, France.
authors: Sophie
authors: S
authors: Langouët
authors: †Masonic Cancer Center and Department of Medicinal Chemistry, Cancer and Cardiology Research Building, University of Minnesota, 2231 6th Street, Minneapolis, Minnesota 55455, United States.
authors: Robert J
authors: RJ
authors: Turesky
mesh_terms: D002273:Carcinogens / Q000032:analysis / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D003296:Cooking; D018736:DNA Adducts / Q000737:chemistry / Q000378:metabolism*; D022781:Hepatocytes / Q000737:chemistry / Q000187:drug effects* / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000032:analysis / Q000378:metabolism*; D008958:Models, Molecular; D010084:Oxidation-Reduction; D012709:Serum Albumin / Q000737:chemistry / Q000378:metabolism*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D002273:Carcinogens; D018736:DNA Adducts; D007093:Imidazoles; D012709:Serum Albumin; C049584:2-amino-1-methyl-6-phenylimidazo(4,5-b)pyridine