THE REACTION OF S-NITROSOGLUTATHIONE WITH SUPEROXIDE

The nitric oxide (NO)-dependent S-nitrosation of thiols to generate S- nitrosothiols has been proposed as an important pathway for the metabo lism of NO in vivo, Although it has been suggested that these S-nitros ated compounds are resistant to decomposition by reactive oxygen metab olites (ROMs), very little information is available regarding the inte raction between S-nitrosothiols and ROMs. We found that S-nitrosogluta thione (GSNO) rapidly reacted with O-2(-) to generate glutathione disu lfide and equimolar quantities of nitrite and nitrate, The reaction wa s second order with respect of GSNO and first order with respect of O- 2(-) with a rate equation of -d[GSNO]/dt = 2k(3)[GSNO](2)[O-2(-)], whe re k(3) = 3 - 6x10(8) M(-2)s(-1), I, addition, the reaction of GSNO wi th O-2(-) generated a strong oxidant as an intermediate capable of oxi dizing dihydrorhodamine in the absence of the apparent generation of N O, We conclude that O-2(-) may act as a physiological modulator of S-n itrosation reactions by directly promoting the decomposition of S-nitr osothiols. (C) 1998 Academic Press.