Members of this family are involved in cobalamin synthesis. Synechocystis sp. cbiH represents a fusion between cbiH and cbiG. As other multi-functional proteins involved in cobalamin biosynthesis catalyze adjacent steps in the pathway, including CysG, CobL (CbiET), CobIJ and CobA-HemD, it is therefore possible that CbiG catalyzes a reaction step adjacent to CbiH. In the anaerobic pathway such a step could be the formation of a gamma lactone, which is thought to help to mediate the anaerobic ring contraction process.
Jiyao W et al.(2023). "The conserved domain database in 2023.",