Rhodanese

Rhodanese, also known as rhodanase, thiosulfate sulfurtransferase, thiosulfate cyanide transsulfurase, and thiosulfate thiotransferase, is a mitochondrial enzyme that detoxifies cyanide (CN⁻) by converting it to thiocyanate (SCN⁻).

This reaction takes place in two steps. The diagram on the right shows the crystallographically-determined structure of rhodanese. In the first step, thiosulfate reacts with the thiol group on cysteine-247 1, to form a persulfide 2. In the second step, the disulfide reacts with cyanide to produce thiocyanate, itself being converted back into the "normal" thiol 1.

This reaction is important for the treatment of exposure to cyanide, since the thiocyanate formed is less toxic. The use of thiosulfate solution as an antidote for cyanide poisoning is based on the activation of this enzymatic cycle.

Rhodanese shares evolutionary relationship with a large family of proteins, including