Rhodanese

Rhodanese-like domain
Crystallographically-determined structure of rhodanese (PDB: 1BOH​)
Identifiers
Symbol	Rhodanese
Pfam	PF00581
InterPro	IPR001763
PROSITE	PDOC00322
SCOP2	2ora / SCOPe / SUPFAM
OPM superfamily	413
OPM protein	2mpn
CDD	cd00158
Membranome	571
Available protein structures: PDB   IPR001763 PF00581 (ECOD; PDBsum)   AlphaFold IPR001763 PF00581

Rhodanese is a mitochondrial enzyme that detoxifies cyanide (CN⁻) by converting it to thiocyanate (SCN⁻, also known as "rhodanate"). In enzymatology, the common name is listed as thiosulfate sulfurtransferase (EC 2.8.1.1). It catalyzes the following reaction:

thiosulfate + cyanide ${\displaystyle \rightleftharpoons }$ sulfite + thiocyanate

Structure and mechanism

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 hydropersulfide 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.

While cyanide is the most well-characterized sulfur acceptor from rhodanese, biological thiols such as glutathione are capable of acting as acceptors to form free low-molecular weight hydropersulfides such as glutathione hydropersulfide.

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

External links

Wikimedia Commons has media related to Rhodanese.

• Rhodanese at the U.S. National Library of Medicine Medical Subject Headings (MeSH)