Rhodanese is a mitochondrialenzyme that detoxifies cyanide (CN−) by converting it to thiocyanate (SCN−, also known as "rhodanate").[1] In enzymatology, the common name is listed as thiosulfate sulfurtransferase (EC2.8.1.1).[2] The diagram on the right shows the crystallographically-determined structure of rhodanese.
This reaction takes place in two steps. 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 thiol1.[3]
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[4]
Rhodanese has an internal duplication. This domain is found as a single copy in other proteins, including phosphatases and ubiquitin C-terminal hydrolases.[5]
This reaction is important for the treatment of exposure to cyanide, since the thiocyanate formed is around 1 / 200 as toxic.[6]:p. 15938 The use of thiosulfate solution as an antidote for cyanide poisoning is based on the activation of this enzymatic cycle.
The following other human genes match the "Rhodanese-like" domain on InterPro, but are not the rodanase with its catalytic activity (see also the list of related families in #Structure and mechanism):
Although the standard nomenclature rules for enzymes indicate that their names are to end with the letters "-ase", rhodanese was first described in 1933,[7] prior to the 1955 establishment of the Enzyme Commission; as such, the older name had already attained widespread usage.
The systematic name of this enzyme class is "thiosulfate:cyanide sulfurtransferase". Other names in common use include "thiosulfate cyanide transsulfurase", "thiosulfate thiotransferase", "rhodanese", and "rhodanase".
sulfite + thiocyanate
