Information on EC 2.8.1.6 - biotin synthase

The enzyme binds a [4Fe-4S] and a [2Fe-2S] cluster. In every reaction cycle, the enzyme consumes two molecules of AdoMet. The first reaction produces 5′-deoxyadenosine and 4,5-secobiotin. Reaction with another equivalent of AdoMet results in abstraction of the C-6 methylene pro-S hydrogen atom from 4,5-secobiotin, and the resulting carbon radical is quenched via formation of an intramolecular C-S bond, thus closing the biotin tetrahydrothiophene 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.