Highly purified biotin synthase can transform dethiobiotin into biotin in the absence of any other protein, in the presence of photoreduced deazaflavin.

Biotin synthase from Bacillus sphaericus has been purified to homogeneity from a recombinant strain. The UV-visible spectrum of the pure protein reveals the presence of a [2Fe-2S] cluster. The enzyme is active in the conversion of dethiobiotin to biotin in vitro, in the presence of NADPH, AdoMet and additional unidentified components from the crude extract of B. sphaericus wild type. We have also found that photoreduced deazaflavin can substitute for the crude extract and NADPH. In this system, biotin synthase is capable of transforming dethiobiotin into biotin in the absence of any other protein but at a substoichiometric level. When this assay was conducted in the presence of [35S]cysteine, no 35S was incorporated into biotin, contrary to what happens in the presence of the crude extract.