title: Nitric oxide-related species-induced protein oxidation: reversible, irreversible, and protective effects on enzyme function of papain.
abstract: Protein oxidation, irreversible modification, and inactivation may play key roles in various neurodegenerative disorders. Therefore, we studied the effects of the potentially in vivo occurring nitric oxide-related species on two different markers of protein oxidation: protein carbonyl generation on bovine serum albumine (BSA) and loss of activity of a cysteine-dependent protease, papain, in vitro by using Angeli's salt, papanonoate, SIN-1, and S-nitrosoglutathione (GSNO) as donors of nitroxyl, nitric oxide, peroxynitrite, and nitrosonium ions, respectively. Angeli's salt, SIN-1, and papanonoate (0-1000 microM) all generated a concentration-dependent increase in carbonyl formation on BSA (107, 60, and 45%, respectively). GSNO did not affect carbonyl formation. Papain was inhibited by Angeli's salt, SIN-1, papanonoate, and GSNO with IC50 values of 0.62, 2.3, 54, and 80 microM, respectively. Angeli's salt (3.16 microM)-induced papain inactivation was only partially reversible, while the effects of GSNO (316 microM) and papanonoate (316 microM) were reversible upon addition of excess DTT. The Angeli's salt-mediated DTT-irreversible inhibition of papain was prevented by GSNO or papanonoate pretreatment, hypothetically through mixed disulfide formation or S-nitrosylation of the catalytically critical thiol group of papain. These results, for the first time, compare the generation of carbonyls in proteins by Angeli's salt, papanonoate, and SIN-1. Furthermore, these results suggest that S-nitrosothiols may have a novel function in protecting critical thiols from irreversible oxidative damage.
authors.affiliation: Institute of Biomedicine (Pharmacology), Biomedicum Helsinki, P.O. Box 63, University of Helsinki 00014, Finland.
authors.forename: Antti J
authors.initials: AJ
authors.lastname: Väänänen
authors.forename: Esko
authors.initials: E
authors.lastname: Kankuri
authors.forename: Pekka
authors.initials: P
authors.lastname: Rauhala
mesh_terms: D000975:Antioxidants / Q000494:pharmacology; D009569:Nitric Oxide / Q000502:physiology*; D010084:Oxidation-Reduction; D010206:Papain / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013438:Sulfhydryl Compounds / Q000378:metabolism
chemical_list: D000975:Antioxidants; D013438:Sulfhydryl Compounds; D009569:Nitric Oxide; D010206:Papain