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 thiol 1. 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 Rhodanese has an internal duplication. This domain is found as a single copy in other proteins, including phosphatases and ubiquitin C-terminal hydrolases. ==Clinical relevance==

This reaction is important for the treatment of exposure to cyanide, since the thiocyanate formed is around 1 / 200 as toxic.:p. 15938 The use of thiosulfate solution as an antidote for cyanide poisoning is based on the activation of this enzymatic cycle. ==Human proteins==

The human mitochondrial rhodanese gene is TST. 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): • M-phase inducer phosphatase: CDC25A; CDC25B; CDC25C; • Dual specificity protein phosphatase: DUSP; DUSP1; DUSP2; DUSP4; DUSP5; DUSP6; DUSP7; DUSP10; DUSP16, aka MKP7; • Thiosulfate:glutathione sulfurtransferase: KAT, now known as "TSTD1"; • Adenylyltransferase and sulfurtransferase: MOCS3; • 3-mercaptopyruvate sulfurtransferase: MPST, also known as "TSTD2" • Not an enzyme: TBCK; TSGA14; • Ubiquitin carboxyl-terminal hydrolase: USP8; • Unknown activity: TSTD3 ==Nomenclature==

Although the standard nomenclature rules for enzymes indicate that their names are to end with the letters "-ase", rhodanese was first described in 1933, 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". Probably from ῥόδον (ródon), meaning rose, in reference to rhodanic acid which has a red colour with ferric salts. ==References==