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.[medical citation needed] 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 <db_xref db="INTERPRO" dbkey="IPR001307" />).
Rhodanese has an internal duplication. This domain is found as a single copy in other proteins, including phosphatases and ubiquitin C-terminal hydrolases.
Human proteins containing this domain
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.
- EC 18.104.22.168, at the International Union of Biochemistry and Molecular Biology
- Cipollone R, Ascenzi P, Tomao P, Imperi F, Visca P (2008). "Enzymatic detoxification of cyanide: clues from Pseudomonas aeruginosa Rhodanese". J. Mol. Microbiol. Biotechnol. 15 (2-3): 199–211. doi:10.1159/000121331. PMID 18685272.
- Gliubich F, Gazerro M, Zanotti G, Delbono S, Bombieri G, Berni R (1996). "Active site structural features for chemically modified forms of rhodanese". J. Biol. Chem. 271 (35): 21054–21061. doi:10.1074/jbc.271.35.21054. PMID 8702871.
- Common Themes and Variations in the Rhodanese Superfamily, by Rita Cipollone, Paolo Ascenzi, and Paolo Visca, in IUBMB Life, vol. 59, no. 2 (February 2007); page 51-59; DOI: 10.1080/15216540701206859
- F. Gliubich; M. Gazerro; G. Zanotti; S. Delbono; G. Bombieri; R. Berni (1996). "Active Site Structural Features for Chemically Modified Forms of Rhodanese". Journal of Biological Chemistry. 271 (35): 21054–21061. doi:10.1074/jbc.271.35.21054. PMID 8702871.