Role of redox-active iron ions in the decomposition of S-nitrosocysteine in subcellular fractions of porcine aorta.
We recently reported that degradation of S-nitrosocysteine in homogenates of porcine aorta increased severalfold in the presence of Mg2+ ions [Kostka, P., Xu, B. & Skiles, E.H. (1999) J. Cardiovasc. Pharmacol. 33, 665-670]. The objective of the present study was to examine this in greater detail. The rate of S-nitrosocysteine degradation by aortic homogenates in the presence of Mg2+ ions exhibited differential sensitivity to chelators of iron ions. Terpyridine and diethylenetriamine penta-acetic acid (5-500 microM) caused a concentration-dependent inhibition of S-nitrosocysteine decay, whereas deferoxamine (100 microM) was ineffective. o-Phenanthroline (250 microM), a selective chelator of Fe2+ ions, potentiated the reaction at low initial concentrations of S-nitrosocysteine (< or = 15 microM) and inhibited the reaction at higher concentrations. The inhibitory effects of o-phenanthroline were related to suppression of S-nitrosocysteine decay by cysteine-mediated reduction of Fe3+. In the presence of o-phenanthroline, S-nitrosocysteine decomposition followed saturable kinetics with K0.5 = 3.8 +/- 0.3 microM 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 with lactate dehydrogenase activity. At non-limiting concentrations of S-nitrosocysteine, 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 cytosolic fraction of porcine aorta contains a protein factor, presumably an enzyme, capable of catalyzing heterolytic decomposition of the S-NO bond of S-nitrosocysteine in a process involving redox cycling of iron ions.
Sorenson
E
E
Department of Chemistry, Cleveland State University, OH 44115, USA.
Skiles
E H
EH
Xu
B
B
Aleryani
S
S
Kostka
P
P
D000818:Animals; D001011:Aorta / Q000378:metabolism*; D002614:Chelating Agents / Q000494:pharmacology; D003545:Cysteine / Q000031:analogs & derivatives* / Q000378:metabolism / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D003676:Deferoxamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D007477:Ions; D007501:Iron / Q000378:metabolism*; D007502:Iron Chelating Agents / Q000494:pharmacology; D007700:Kinetics; D007770:L-Lactate Dehydrogenase / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D008956:Models, Chemical; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009603:Nitroso Compounds / Q000378:metabolism*; D004369:Pentetic Acid / Q000494:pharmacology; D010618:Phenanthrolines / Q000494:pharmacology; D011725:Pyridines / Q000494:pharmacology; D026403:S-Nitrosothiols; D013552:Swine; D013997:Time Factors
D002614:Chelating Agents; D007477:Ions; D007502:Iron Chelating Agents; D009603:Nitroso Compounds; D010618:Phenanthrolines; D011725:Pyridines; D026403:S-Nitrosothiols; D004369:Pentetic Acid; C021315:S-nitrosocysteine; D007501:Iron; D007770:L-Lactate Dehydrogenase; C013278:2,2',2''-terpyridine; D008274:Magnesium; D003676:Deferoxamine; D003545:Cysteine; C025205:1,10-phenanthroline