title: Analysis of oxidation process of cholecystokinin octapeptide with reactive oxygen species by high-performance liquid chromatography and subsequent electrospray ionization mass spectrometry.
abstract: The C-terminal octapeptide of cholecystokinin (CCK8) includes some easily oxidizable amino acids. The oxidation of CCK8 by reactive oxygen species (ROS) such as hydrogen peroxide (H(2)O(2)) and hydroxyl radicals (OH(*)) was investigated using reversed-phase high performance liquid chromatography (RP-HPLC) and subsequent electrospray ionization mass spectrometry. The mechanism of oxidation of CCK8 in the H(2)O(2) system differed from that of CCK8 in the Fenton system, in which OH(*) are produced. In the H(2)O(2) system, (28)Met and (31)Met were oxidized to methionine sulfoxide, and no further oxidation or degradation/hydrolysis occurred. On the other hand, in the Fenton system, (28)Met and (31)Met residues were oxidized to methionine sulfone via the formation of methionine sulfoxide. In addition, the oxidized product was observed at the Trp residue but not at the Tyr residue, and small peptide fragments from CCK8 were observed in the Fenton system. From these results, it was concluded that (28)Met and (31)Met residues of CCK8 are susceptible to oxidation by ROS.
authors.affiliation: Department of Analytical Chemistry, Faculty of Pharmaceutical Sciences, Toho University, 2-2-1 Miyama, Funabashi-shi, Chiba 274-8510, Japan.
authors.forename: Hideaki
authors.initials: H
authors.lastname: Ichiba
authors.forename: Mio
authors.initials: M
authors.lastname: Nakamoto
authors.forename: Takehiko
authors.initials: T
authors.lastname: Yajima
authors.forename: Mitsuo
authors.initials: M
authors.lastname: Takayama
authors.forename: Takeshi
authors.initials: T
authors.lastname: Fukushima
mesh_terms: D000596:Amino Acids / Q000737:chemistry; D002851:Chromatography, High Pressure Liquid; D006031:Glycosylation; D006861:Hydrogen Peroxide / Q000737:chemistry; D007501:Iron; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D010766:Phosphorylation; D017382:Reactive Oxygen Species / Q000737:chemistry*; D012844:Sincalide / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization
chemical_list: D000596:Amino Acids; C045076:Fenton's reagent; D016877:Oxidants; D017382:Reactive Oxygen Species; D006861:Hydrogen Peroxide; D007501:Iron; D012844:Sincalide