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 (H2 S) 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 H2 S 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 S -nitrosothiols with H2 S 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 H2 S, 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 PNP+ SSNO- to show that contrary to everything that is claimed for the yellow reaction product of GSNO with H2 S, pure SSNO- decomposes readily in the presence of cyanide, H2 S 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.