IRON IS A CATALYST OF CYSTEINE AND GLUTATHIONE S-NITROSATION ON CONTACT WITH NITRIC-OXIDE IN AQUEOUS-SOLUTIONS AT NEUTRAL PH

S-Nitrosocysteine and S-nitrosoGSH were formed when cysteine or reduce d glutathione in 15 mM Hepes-buffer contacted gaseous nitric oxide at neutral pH for 5 min under anaerobic conditions. On increasing the thi ol concentration from 1 to 50 mM and the NO pressure from 50 to 700 mm Hg, higher yields of the S-nitrosothiols were observed. Simultaneousl y with the synthesis of S-nitrosothiols, dinitrosyl iron complexes (DN IC) between cysteine or GSH and trace iron ions were formed. The addit ion of 20 mu M Fe2+ stimulated the formation of both S-nitrosothiols a nd DNIC. The concentration of S-nitrosothiol formed was 40-50% of the initial thiol concentration. S-Nitrosothiol as well as DNIC formation with or without iron present was completely inhibited by preliminary t reatment of the solutions with the selective Fe2+ chelating agent o-ph enanthroline. Admixed or added iron was found to be a catalyst of S-ni trosothiol formation under these conditions. NO is transformed to NOion which effectively nitrosates thiols in the presence of iron formin g DNIC.