CbiD is essential for cobalamin biosynthesis in both S. typhimurium and B. megaterium, no functional role has been ascribed to the protein. The CbiD protein has a putative S-AdoMet binding site. It is possible that CbiD might have the same role as CobF in undertaking the C-1 methylation and deacylation reactions required during the ring contraction process [1].

1: Cobalamin (vitamin B12) biosynthesis: identification and characterization of a Bacillus megaterium cobI operon. Raux E, Lanois A, Warren MJ, Rambach A, Thermes C; Biochem J 1998;335:159-166. PMID:9742225