Nitrosopersulfide (SSNO) decomposes in the presence of sulfide, cyanide or glutathione to give HSNO/SNO: consequences for the assumed role in cell signalling.

The emergence of hydrogen sulfide (HS) as a new signalling molecule able to control vasodilation, neurotransmission and immune response, prompted questions about its possible cross-talk with the other gasontransmitter, nitric oxide (NO). It has been shown that HS reacts with NO and its metabolites and several potentially biologically active species have been identified. Thionitrous acid (HSNO) was proposed to be an intermediate product of the reaction of -nitrosothiols with HS capable of crossing the membranes and causing further trans-nitrosation of proteins. Alternatively, formation of nitrosopersulfide (SSNO) has been proposed in this reaction. SSNO was claimed to be particularly stable and inert to HS, thiols and cyanides. It is suggested that this putative SSNO slowly decomposes to give NO, HNO and polysulfides. However, the chemical studies with pure SSNO salts showed some conflicting observations. In this study, we work with pure PNPSSNO to show that contrary to everything that is claimed for the yellow reaction product of GSNO with HS, pure SSNO decomposes readily in the presence of cyanide, HS and glutathione to form SNO. Based on literature overview and chemical data about the structures of HSNO/SNO and SSNO we discuss the biological role these two species could have.