| Type: | Family | Name: | Adenosylcobalamin biosynthesis, ATP:cob(I)alamin adenosyltransferase, bifunctional PduO |
| Description: | ATP:cob(I)alamin (or ATP:corrinoid) adenosyltransferases (), catalyse the conversion of cobalamin (vitamin B12) into its coenzyme form, adenosylcobalamin (AdoCbl)or coenzyme B12 []. AdoCbl contains an adenosyl moiety liganded to the cobalt ion of cobalamin via a covalent Co-C bond. AdoCbl is required as a cofactor for the activity of certain enzymes. ATP:cob(I)alamin adenosyltransferases are classed into three groups: CobA-type [], EutT-type [] and PduO-type []. Each of the three enzyme types appears to be specialised for particular AdoCbl-dependent enzymes or for the de novo synthesis AdoCbl. PduO and EutT are distantly related, sharing short conserved motifs, while CobA is evolutionarily unrelated and is an example of convergent evolution. This entry represents a bifunctional form of PduO-type ATP:cob(I)alamin adenosyltransferases, as well as other bifunctional proteins with an ATP:cob(I)alamin adenosyltransferase domain. PduO functions to convert inactive cobalamin to adenosylcobalamin (AdoCbl) for 1,2-propanediol degradation []. Members of this family catalyse one of the steps in this process of assimilation of the exogenous inactive cobalamin []. Cobalamin-dependent 1,2-propanediol utilization and glycerol utilization pathways both require AdoCbl for AdoCbl-dependent diol or glycerol dehydratases. PduO is encoded by the propanediol utilization pdu operon.Human and bovine PduO-type ATP:cob(I)alamin adenosyltransferases have been cloned based on homology to PduO and have been shown to complement an ATR-deficient Salmonella mutant []. The human enzyme (MMAB) has been found to correspond to the previously known cblB complementation group of the methylmalonic aciduria disorder. The methylmalonic acidurias are metabolic disorders resulting from the deficient activity of methylmalonyl-CoA mutase, an AdoCbl-dependent enzyme. CblB complementation group have long been known to be caused by deficient activity of a cob(I)alamin adenosyltransferase [].Proteins identified in this entry contain two domains, N- and C-terminal domains, both of which occur in a stand-alone forms. Therefore, PduO and other proteins have been suggested to be bifunctional enzymes that catalyse sequential steps in the adenosylation pathway, namely, the reduction of cob(II)alamin to cob(I)alamin and the adenosylation of cob(I)alamin []. The N-terminal domain is responsible for the ATP:cob(I)alamin adenosyltransferase activity. The C-terminal domain is predicted to have a different enzymatic activity involving the same process: biosynthesis of an active AdoCbl cofactor. | Short Name: | AdoCbl_syn_CblAdoTrfase_bifunc |
