Enzymatic Conversion of Dethiobiotin to Biotin in Cell-free Extracts of a Bacillus sphaericus bioB Transformant

The activity of biotin synthase, responsible for biotin synthesis from dethiobiotin, was demonstrated in a completely defined reaction mixture with cell-free extracts of a Bacillus sphaericus bioB transformant. Among the sulfur compounds tested, only S-adenosyl-l-methionine was active, while l-methionine and l-cysteine had no significant effect. Protein concentrations higher than 15mg/ml in the reaction mixture were needed to detect biotin synthase activity. When dialyzed cell-free extracts were used for the reaction, NADH, NADPH, or FAD among the well-known cofactors tested enhanced the activity, and Fe²⁺, Mn²⁺, and Ca²⁺ among the metal ions tested also had some effects.