Degradation of S-nitrosocysteine in vascular tissue homogenates: role of divalent ions.
The objective of the study was to inquire about the mechanism(s) involved in the catabolism of S-nitrosothiols by vascular tissue under in vitro conditions. Incubations of S-nitrosocysteine (CYSNO) or S-nitrosoglutathione (GSNO) with homogenates isolated from porcine aortic smooth muscle resulted in only a marginal depletion of S-nitrosothiols from the reaction mixtures, which became statistically significant at relatively high concentrations of homogenate (> or =300 microg of protein/ml). Degradation of CYSNO (but not GSNO) was found to be potentiated several-fold by millimolar concentrations of either Mg2+ or Ca2+ ions. Under such conditions, the degradation of CYSNO was significantly suppressed by the removal of proteins by ultrafiltration (>80% inhibition) and eliminated completely by the alkylation of thiol groups with 1 mM N-ethylmaleimide. The potentiating effect of divalent ions on the degradation of CYSNO was insensitive to 0.1 mM neocuproine (selective chelator of Cu+ ions), although it was enhanced in the presence of 0.1 mM o-phenanthroline (selective chelator of Fe2+ ions). It is concluded that the degradation of CYSNO by tissue homogenate involves the interaction with protein-bound sulfhydryl groups, which is stimulated by Mg2+ or Ca2+ ions. The potentiating effect of o-phenanthroline suggests that the liberation of the nitrosonium moiety in such a process may be accompanied by its transfer to sulfur center(s) by transient formation of dinitrosyl-iron complexes.
Kostka
P
P
Department of Chemistry, Cleveland State University, Ohio 44115, USA.
Xu
B
B
Skiles
E H
EH
D000818:Animals; D001011:Aorta / Q000378:metabolism; D002118:Calcium / Q000378:metabolism; D003545:Cysteine / Q000031:analogs & derivatives* / Q000378:metabolism; D005978:Glutathione / Q000031:analogs & derivatives* / Q000378:metabolism; D008274:Magnesium / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009603:Nitroso Compounds / Q000378:metabolism*; D026422:S-Nitrosoglutathione; D026403:S-Nitrosothiols; D013552:Swine
D009603:Nitroso Compounds; D026403:S-Nitrosothiols; D026422:S-Nitrosoglutathione; C021315:S-nitrosocysteine; D005978:Glutathione; D008274:Magnesium; D003545:Cysteine; D002118:Calcium