InterPro domain: IPR024177

This family consists of biotin synthase B-like proteins.

Biotin synthase 2.8.1.6 works with flavodoxin, S-adenosylmethionine, and possibly cysteine to catalyze the last step of the biotin biosynthetic pathway. The reaction consists of the introduction of a sulphur atom intodethiobiotin, thus requiring activation of C-H bonds [ 1 ]. Biotin (vitamin H) is a prosthetic group in enzymes catalysing carboxylation and transcarboxylation reactions [ 2 ].

Biotin synthase from Escherichia coli is a homodimer of 76kDa, with each polypeptidechain carrying an oxygen-sensitive (4Fe-4S) cluster, probably ligated by three cysteines of a CXXXCXXC box conserved among all known BioB sequencesand a fourth still not identified ligand. BioB displays a pyridoxal phosphate-dependent cysteine desulphurase activity, which allows mobilisation of thesulphur atom from free cysteine [ 3 ].

1. Cloning, sequencing, and characterization of the Bacillus subtilis biotin biosynthetic operon. J. Bacteriol. 178, 4122-30
2. Two new members of the bio B superfamily: cloning, sequencing and expression of bio B genes of Methylobacillus flagellatum and Corynebacterium glutamicum. Gene 175, 15-22
3. Biotin synthase is a pyridoxal phosphate-dependent cysteine desulfurase. Biochemistry 41, 9145-52