title: One-electron reduction of selenomethionine oxide.
abstract: Experimental evidence is provided that selenomethionine oxide (MetSeO) is more readily reducible than its sulfur analogue, methionine sulfoxide (MetSO). Pulse radiolysis experiments reveal an efficient reaction of MetSeO with one-electron reductants, such as e(aq)-, (k = 1.2x10(10) M(-1) s(-1)), CO2*- (k = 5.9x10(8) M(-1) s(-1)) and (CH3)2 C*OH (k = 3.5x10(7) M(-1) s(-1)), forming an intermediate selenium-nitrogen coupled zwitterionic radical with the positive charge at an intramolecularly formed Se(three-electron bond)N 2sigma/1sigma* three-electron bond, which is characterized by an optical absorption with lambda(max) at 375 nm, and a half-life of about 70 micros. The same transient is generated upon HO* radical-induced one-electron oxidation of selenomethionine (MetSe). This radical thus constitutes the redox intermediate between the two oxidation states, MetSeO and MetSe. Time-resolved optical data further indicate sulfur-selenium interactions between the Se(three-electron bond)N transient and GSH. The Se(three-electron bond)N transient appears to play a key role in the reduction of selenomethionine oxide by glutathione.
authors.affiliation: Institut für Physiologische Chemie I, Heinrich-Heine-Universität Düsseldorf, Germany.
authors.forename: A
authors.initials: A
authors.lastname: Assmann
authors.forename: M
authors.initials: M
authors.lastname: Bonifacić
authors.forename: K
authors.initials: K
authors.lastname: Briviba
authors.forename: H
authors.initials: H
authors.lastname: Sies
authors.forename: K D
authors.initials: KD
authors.lastname: Asmus
mesh_terms: D055598:Chemical Phenomena; D002627:Chemistry, Physical; D004583:Electrons; D005978:Glutathione / Q000737:chemistry; D017665:Hydroxyl Radical / Q000737:chemistry; D007700:Kinetics; D010084:Oxidation-Reduction; D011675:Pulse Radiolysis; D012645:Selenomethionine / Q000737:chemistry*; D012996:Solutions; D013053:Spectrophotometry; D014867:Water
chemical_list: D012996:Solutions; D014867:Water; D017665:Hydroxyl Radical; D012645:Selenomethionine; D005978:Glutathione