Overview for MACiE Entry M0284
EC Number: 22.214.171.124 (A member of the Hydrolases, Acting on carbon-nitrogen bonds, other than peptide bonds, In nitriles)
Enzyme Name: thiocyanate hydrolase
Biological Species: Thiobacillus thioparus (Bacteria)
Catalytic Chain UniprotKB Accession Codes:
- O66188 - Thiocyanate hydrolase subunit gamma
Representative PDB Code: 2dd5 - THIOCYANATE HYDROLASE (SCNASE) FROM THIOBACILLUS THIOPARUSNATIVE HOLO-ENZYME (Resolution = 2.00 Å).
Catalytic CATH Codes:
"Other" CATH Codes:
Display structure information
Overall Comment: Thiocyanate hydrolase catalyses the degradation of thiocyanate to carbonyl sulfide and ammonia. An alternative mechanism, involving enzyme-substrate covalent intermediates has been suggested, although no evidence is available to support the existence of such species . Structural studies show all three chains to surround the active site, with positive side chains projecting towards the metal centre from each of them, stabilising the negatively charged substrate and product .
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Stepwise Description of the Reaction
|Step 1||Tyr108 activates a water molecule towards nucleophilic attack on the Co(III) coordinated thiocyanate substrate.|
|Step 2||A proton is exchanged between the hydrolysis product and Tyr108C.|
|Step 3||Tautomerisation of the intermediate results in a carbonyl species.|
|Step 4||An internal proton transfer occurs.|
|Step 5||The hydroxyl present on Cys133 activates a water molecule to act as a nucleophile towards the thio-acid intermediate.|
|Step 6||The tetrahedral anion collapses resulting in concomitant release of ammonia and deprotonation of Cys133.|
|Step 7||An intermolecular elimination of hydroxide occurs, forming carbonyl sulfide.|
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Catalytic Residues Involved
||Location of Function
||Main Chain Amide
Post-translationally modified residue
Main Chain Amide
||Post-translationally modified residue
Metal Cofactors for M0284
- T. Arakawa et al. (2007), J. Mol. Biol., 366, 1497-1509. Structure of thiocyanate hydrolase: a new nitrile hydratase family protein with a novel five-coordinate cobalt(III) center.
- N. Gupta et al. (0), J. Hazard Mater., 176, 1-13. .
- T. Arakawa et al. (2009), J. Am. Chem. Soc., 131, 4838-4843. Structural Basis for Catalytic Activation of Thiocyanate Hydrolase Involving Metal-Ligated Cysteine Modification.
- Y. Katayama et al. (1998), J. Bacteriol., 180, 2583-2589. Cloning of genes coding for the three subunits of thiocyanate hydrolase of Thiobacillus thioparus THI 115 and their evolutionary relationships to nitrile hydratase.
Homologue information for M0284 (2dd5)
MACiE Homologues (within the PDB)
MACiE Homologues (within UniprotKB/SwissProt)
Links to this entry in other databases