What is "rhodanese"

n. (context enzyme English) A mitochondrial enzyme that catalyzes the conversion of cyanide to thiocyanate

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 is reduced by the thiol group on cysteine-247 1, to form a persulfide and a sulfite 2. In the second step, the persulfide reacts with cyanide to produce thiocyanate, re-generating the cysteine 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

• Cdc25 phosphatase catalytic domain.
• non-catalytic domains of eukaryotic dual-specificity MAPK-phosphatases
• non-catalytic domains of yeast PTP-type MAPK-phosphatases
• non-catalytic domains of yeast Ubp4, Ubp5, Ubp7
• non-catalytic domains of mammalian Ubp-Y
• Drosophila heat shock protein HSP-67BB
• several bacterial cold-shock and phage shock proteins
• plant senescence associated proteins
• catalytic and non-catalytic domains of rhodanese (see ).

Rhodanese has an internal duplication. This domain is found as a single copy in other proteins, including phosphatases and ubiquitin C-terminal hydrolases.