Reaction: dethiobiotin + sulfur-(sulfur carrier) + 2 S-adenosyl-L-methionine + 2 reduced [2Fe-2S] ferredoxin = biotin + (sulfur carrier) + 2 L-methionine + 2 5'-deoxyadenosine + 2 oxidized [2Fe-2S] ferredoxin
Glossary: biotin = 5[(3aS,4S,6aR)-2-oxohexahydro(4H-thieno[4,5-d]imidazol-4-yl)]pentanoate
4,5-secobiotin = 6-[(4R,5R)-2-oxo-5-(sulfanylmethyl)imidazolidin-4-yl]hexanoate = 9-mercaptodethiobiotin
Other name(s): dethiobiotin:sulfur sulfurtransferase
Systematic name: dethiobiotin:sulfur-(sulfur carrier) sulfurtransferase
Comments: The enzyme binds a [4Fe-4S] and a [2Fe-2S] cluster. In every reaction cycle, the enzyme consumes two molecules of AdoMet, each producing 5'-deoxyadenosine and a putative dethiobiotinyl carbon radical. Reaction with another equivalent of AdoMet results in abstraction of the C-6 methylene pro-S hydrogen atom from 9-mercaptodethiobiotin, and the resulting carbon radical is quenched via formation of an intramolecular C-S bond, thus closing the biotin thiophane ring. The sulfur donor is believed to be the [2Fe-2S] cluster, which is sacrificed in the process, so that in vitro the reaction is a single turnover. In vivo, the [2Fe-2S] cluster can be reassembled by the Isc or Suf iron-sulfur cluster assembly systems, to allow further catalysis.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 80146-93-6
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