Kinetics of peroxynitrite reaction with amino acids and human serum albumin

Abstract

S-Nitrosoalbumin (SNOALB) is the most abundant physiological circulating nitric oxide (NO) carrier regulating NO-dependent biological actions in humans. The mechanisms of its formation and biological actions are still incompletely understood. Nitrosation by authentic NO and S-transnitrosylation of the single sulfhydryl group located at Cys-34 of human albumin by the physiological S-nitroso compounds S-nitrosocysteine (SNOC) and S-nitrosoglutathione (GSNO) are two possible mechanisms. On a quantitative basis, we investigated by gas chromatography-mass spectrometry the contribution of these two mechanisms to SNOALB formation in human plasma and blood in vitro. GSNO and SNOC (0–100 μM) rapidly and efficiently (recovery=35%) S-transnitrosylated albumin to form SNOALB. NO (100 μM) S-nitrosated albumin to SNOALB at a considerably lower extent (recovery=5%). The putative NO-donating drugs glyceryl trinitrate and sodium nitroprusside (each 100 μM) failed completely in S-nitrosating albumin. Bubbling NO into human plasma and blood resulted in formation of SNOALB that inhibited ADP-induced platelet aggregation. Infusion of GS15NO in the rat resulted in formation of S15NOALB, [15N]nitrate and [15N]nitrite. Our results suggest that S-transnitrosylation of albumin by SNOC and GSNO could be a more favored mechanism for the formation of SNOALB in the circulation in vivo than S-nitrosation of albumin by NO itself.