title: Is novel signal transducer sulfur oxide involved in the redox cycle of persulfide at the catalytic site cysteine in a stable reaction intermediate of mercaptopyruvate sulfurtransferase?
abstract: Abstract In transsulfuration reaction catalyzed by rat mercaptopyruvate sulfurtransferase (MST), a stable persulfide is formed at the catalytic site cysteine Cys(247) as a reaction intermediate. The outer sulfur atom is donated by the substrate, thiosulfate, or by mercaptopyruvate. MST serves as a thioredoxin-dependent antioxidant possessing self-regulated enzymatic activity. After oxidation of persulfurated MST by treatment with hydrogen peroxide, mass spectrometric analysis showed that the outer sulfur atom of the persulfide is oxidized to form Cys-thiosulfenate (Cys-Sγ-SO(-)), Cys-thiosulfinate (Cys-Sγ-SO(2)(-)), and Cys-thiosulfonate (Cys-Sγ-SO(3)(-)). Next, sulfur acceptor substrates including reduced thioredoxin convert all modified cysteines to nonmodified cysteines. Another sulfur acceptor substrate, cyanide, also converted these cysteines via cyanolysis. Thus, sulfur oxides are suggested to release in the redox cycle of persulfide of MST.
authors.affiliation: Department of Environmental Medicine, Nippon Medical School, Tokyo, Japan. noriyuki@nms.ac.jp
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Nagahara
authors.forename: Takashi
authors.initials: T
authors.lastname: Nirasawa
authors.forename: Taro
authors.initials: T
authors.lastname: Yoshii
authors.forename: Youichi
authors.initials: Y
authors.lastname: Niimura
mesh_terms: D000818:Animals; D020134:Catalytic Domain; D003486:Cyanides / Q000737:chemistry; D003545:Cysteine / Q000737:chemistry*; D006861:Hydrogen Peroxide / Q000737:chemistry; D016877:Oxidants / Q000737:chemistry; D010084:Oxidation-Reduction; D010087:Oxides / Q000737:chemistry*; D051381:Rats; D019163:Reducing Agents / Q000737:chemistry; D015398:Signal Transduction; D013440:Sulfides / Q000737:chemistry*; D013457:Sulfur Compounds / Q000737:chemistry*; D013466:Sulfurtransferases / Q000737:chemistry*; D013879:Thioredoxins / Q000737:chemistry
chemical_list: D003486:Cyanides; D016877:Oxidants; D010087:Oxides; D019163:Reducing Agents; D013440:Sulfides; D013457:Sulfur Compounds; C051552:persulfides; C405951:sulfur monoxide; D013879:Thioredoxins; D006861:Hydrogen Peroxide; D013466:Sulfurtransferases; C021550:3-mercaptopyruvate sulphurtransferase; D003545:Cysteine