Linked Life Data

9525875

Source:http://linkedlifedata.com/resource/pubmed/id/9525875

Statements in which the resource exists as a subject.
PredicateObject
rdf:type
lifeskim:mentions
pubmed:issue
14
pubmed:dateCreated
1998-5-7
pubmed:abstractText
S-Nitrosothiols (RSNO) occur in vivo and have been proposed as nitric oxide (.NO) storage and transport biomolecules. Still, the biochemical mechanisms by which RSNO release .NO in biological systems are not well defined, and in particular, the interactions between reactive oxygen species and RSNO have not been studied. In this work, we show that xanthine oxidase (XO), in the presence of purine (hypoxanthine, xanthine) or pteridine (lumazine) substrates, induces S-nitrosocysteine (CysNO) and S-nitrosoglutathione (GSNO) decomposition under aerobic conditions. The decomposition of RSNO by XO was inhibitable by copper-zinc superoxide dismutase, in agreement with the participation of superoxide anion (O-2) in the process. However, while superoxide dismutase could totally inhibit aerobic decomposition of GSNO, it was only partially inhibitory for CysNO. Competition experiments indicated that O-2 reacted with GSNO with a rate constant of 1 x 10(4) M-1.s-1 at pH 7.4 and 25 degreesC. The decomposition of RSNO was accompanied by peroxynitrite formation as assessed by the oxidation of dihydrorhodamine and of cytochrome c2+. The proposed mechanism involves the O-2-dependent reduction of RSNO to yield .NO, which in turn reacts fast with a second O-2 molecule to yield peroxynitrite. Under anaerobic conditions, CysNO incubated with xanthine plus XO resulted in CysNO decomposition, .NO detection, and cysteine and uric acid formation. We found that CysNO is an electron acceptor substrate for XO with a Km of 0.7 mM. In agreement with this concept, the enzymatic reduction of CysNO by XO was inhibitable by oxypurinol and diphenyliodonium, inhibitors that interfere with the catalytic cycle at the molybdenum and flavin sites, respectively. In conclusion, XO decomposes RSNO by O-2-dependent and -independent pathways, and in the presence of oxygen it leads to peroxynitrite formation.
pubmed:grant
pubmed:language
eng
pubmed:journal
pubmed:citationSubset
IM
pubmed:chemical
pubmed:status
MEDLINE
pubmed:month
Apr
pubmed:issn
0021-9258
pubmed:author
pubmed:issnType
Print
pubmed:day
3
pubmed:volume
273
pubmed:owner
NLM
pubmed:authorsComplete
Y
pubmed:pagination
7828-34
pubmed:dateRevised
2007-11-15
pubmed:meshHeading
pubmed:year
1998
pubmed:articleTitle
Xanthine oxidase-mediated decomposition of S-nitrosothiols.
pubmed:affiliation
Departamento de Bioquímica, Facultad de Medicina, Universidad de la República, Montevideo 11800, Uruguay.
pubmed:publicationType
Journal Article, Research Support, U.S. Gov't, P.H.S., Research Support, Non-U.S. Gov't