Role of redox-active iron ions in the decomposition of S-nitrosocysteine in subcellular fractions of porcine aorta

Citation
E. Sorenson et al., Role of redox-active iron ions in the decomposition of S-nitrosocysteine in subcellular fractions of porcine aorta, EUR J BIOCH, 267(14), 2000, pp. 4593-4599
Citations number
13
Language
INGLESE
art.tipo
Article
Categorie Soggetti
Biochemistry & Biophysics
Journal title
EUROPEAN JOURNAL OF BIOCHEMISTRY
ISSN journal
0014-2956 → ACNP
Volume
267
Issue
14
Year of publication
2000
Pages
4593 - 4599
Database
ISI
SICI code
0014-2956(200007)267:14<4593:RORIII>2.0.ZU;2-O
Abstract
We recently reported that degradation of S-nitrosocysteine in homogenates o f porcine aorta increased severalfold in the presence of Mg2+ ions [Kostka, P., Xu, B. & Skiles, E.H. (1999) J. Cardiovasc. Pharmacol. 33, 665-670]. T he objective of the present study was to examine this in greater detail. Th e rate of S-nitrosocysteine degradation by aortic homogenates in the presen ce of Mg2+ ions exhibited differential sensitivity to chelators of iron ion s. Terpyridine and diethylenetriamine penta-acetic acid (5-500 mu M) caused a concentration-dependent inhibition of S-nitrosocysteine decay, whereas d eferoxamine (100 mu M) was ineffective. o-Phenanthroline (250 mu M), a sele ctive chelator of Fe2+ ions, potentiated the reaction at low initial concen trations of S-nitrosocysteine (less than or equal to 15 mu M) and inhibited the reaction at higher concentrations. The inhibitory effects of o-phenant hroline were related to suppression of S-nitrosocysteine decay by cysteine- mediated reduction of Fe3+. In the presence of o-phenanthroline, S-nitrosoc ysteine decomposition followed saturable kinetics with K-0.5 = 3.8 +/- 0.3 mu M and h = 1.8 +/- 0.1 (mean +/- SE, n = 4). Comparison of the rates of S -nitrosocysteine decay in different subcellular fractions showed selective association with the cytosolic fraction, as documented by copurification wi th lactate dehydrogenase activity. At non-limiting concentrations of S-nitr osocysteine, the rate of degradation in the cytosolic fraction was 4.1 +/- 0.3 nmol.min(-1).(mg protein)(-1) (n = 4). It is concluded that the cytosol ic fraction of porcine aorta contains a protein factor, presumably an enzym e, capable of catalyzing heterolytic decomposition of the S-NO bond of S-ni trosocysteine in a process involving redox cycling of iron ions.