Sulfur-to-nitrogen transnitrosation: transfer of nitric oxide from S-nitroso compounds to diethanolamine and the role of intermediate sulfur-to-sulfur transnitrosation

S-Nitrosothiols are formed in vivo and are involved in NO signaling. We inv estigated the sulfur-to-nitrogen transnitrosation activity of S-nitrosocyst eine. S-nitrosoglutathione, S-nitrosohomocysteine, S-nitrusocysteinylglycin e and S-nitroso-N-acerylcysteine in their reaction with the secondary amine diethanolamine in vitro. The resulting N-nitrosodiethanolamine, a strong c arcinogen. was formed in yields of up to 11% from S-nitrosocysteine and S-n itrosocysteinylglycine, whereas the transnitrosation activity of the other S-nitroso compounds was weak. However. the addition of L-cysteine to a solu tion of S-nitrosohomocysteine and diethanolamine accelerated the decomposit ion of S-nitrosohomocysteine and resulted in a significant formation of N-n itrosodiethanolamine accompanied by the intermediate generation of S-nitros ocysteine. Thus, reactive nitrosothiols can be formed from less reactive an alogs via sulfur-to-sulfur transnitrosation. We suggest that this affects r egulation of NO trafficking in vivo. The reaction provides an alternative m echanism fur the generation of carcinogenic N-nitroso derivatives. (C) 2001 Elsevier Science Ireland Ltd. All rights reserved.