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Cobalamin synthesis G C-terminus Members of this family are involved in cobalamin synthesis. The protein encoded by 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. Within the cobalamin synthesis pathway CbiG catalyzes the both the opening of the lactone ring and the extrusion of the two-carbon fragment of cobalt-precorrin-5A from C-20 and its associated methyl group (deacylation) to give cobalt-precorrin-5B. This family is the C-terminal region, and the mid- and N-termival parts are conserved independently in other families.
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Lu S et al.(2020). "CDD/SPARCLE: the conserved domain database in 2020.",