This radical SAM enzyme belongs to the family of transferases, specifically the sulfurtransferases, which transfer sulfur-containing groups.

The protein is a homodimer, meaning it is composed of two identical amino acid chains that fold together to form biotin synthase.

[3] The predicted role of the [4Fe-4S]2+cofactor is to transfer an electron onto SAM through an inner sphere mechanism, forcing it into an unstable high energy state that ultimately leads to the formation of the 5’deoxyadenosyl radical.

Isotopic labelling[5] and spectroscopic studies[6] show destruction of the [2Fe-2S]2+cluster accompanies BioB turnover, indicating that it is likely sulfur from [2Fe-2S]2+that is being incorporated into DTB to form biotin.

This radical attacks the sulfur attached to C9 and forms the thiophane ring of biotin, leaving behind an unstable diferrous cluster that likely dissociates.

At physiological pH, these would all be protonated, and the carbon radical would likely be quenched by hydrogen atom transfer rather than by C-S bond formation.

The amount of E. coli that produce biotin is significantly higher in adults than in babies, indicating that the gut microbiome and developmental stage should be taken into account when assessing a person's nutritional needs.