EC Explorer

2.5.1.17

corrinoid adenosyltransferase

(1) 2 ATP + 2 cob(II)alamin + a reduced flavoprotein = 2 triphosphate + 2 adenosylcob(III)alamin + an oxidized flavoprotein (overall reaction);;(1a) 2 cob(II)alamin + 2 [corrinoid adenosyltransferase] = 2 [corrinoid adenosyltransferase]-cob(II)alamin;;(1b) a reduced flavoprotein + 2 [corrinoid adenosyltransferase]-cob(II)alamin = an oxidized flavoprotein + 2 [corrinoid adenosyltransferase]-cob(I)alamin (spontaneous);;(1c) 2 ATP + 2 [corrinoid adenosyltransferase]-cob(I)alamin = 2 triphosphate + 2 adenosylcob(III)alamin + 2 [corrinoid adenosyltransferase];;(2) 2 ATP + 2 cob(II)yrinic acid a,c-diamide + a reduced flavoprotein = 2 triphosphate + 2 adenosylcob(III)yrinic acid a,c-diamide + an oxidized flavoprotein (overall reaction);;(2a) 2 cob(II)yrinic acid a,c-diamide + 2 [corrinoid adenosyltransferase] = 2 [corrinoid adenosyltransferase]-cob(II)yrinic acid a,c-diamide;;(2b) a reduced flavoprotein + 2 [corrinoid adenosyltransferase]-cob(II)yrinic acid a,c-diamide = an oxidized flavoprotein + 2 [corrinoid adenosyltransferase]-cob(I)yrinic acid a,c-diamide (spontaneous);;(2c) 2 ATP + 2 [corrinoid adenosyltransferase]-cob(I)yrinic acid a,c-diamide = 2 triphosphate + 2 adenosylcob(III)yrinic acid a,c-diamide + 2 [corrinoid adenosyltransferase]

MMAB (gene name), cobA (gene name), cobO (gene name), pduO (gene name), ATP:corrinoid adenosyltransferase, cob(I)alamin adenosyltransferase, aquacob(I)alamin adenosyltransferase, aquocob(I)alamin vitamin B_12s adenosyltransferase, ATP:cob(I)alamin Coβ-adenosyltransferase, ATP:cob(I)yrinic acid-a,c-diamide Coβ-adenosyltransferase, cob(I)yrinic acid a,c-diamide adenosyltransferase

ATP:cob(II)alamin Coβ-adenosyltransferase

37277-84-2

The corrinoid adenosylation pathway comprises three steps: (i) reduction of Co(III) within the corrinoid to Co(II) by a one-electron transfer. This can occur non-enzymically in the presence of dihydroflavin nucleotides or reduced flavoproteins [3]. (ii) Co(II) is bound by corrinoid adenosyltransferase, resulting in displacement of the lower axial ligand by an aromatic residue. The reduction potential of the 4-coordinate Co(II) intermediate is raised by ~250 mV compared with the free compound, bringing it to within physiological range. This is followed by a second single-electron transfer from either free dihydroflavins or the reduced flavin cofactor of flavoproteins, resulting in reduction to Co(I) [7]. (iii) the Co(I) conducts a nucleophilic attack on the adenosyl moiety of ATP, resulting in transfer of the deoxyadenosyl group and oxidation of the cobalt atom to Co(III) state. Three types of corrinoid adenosyltransferases, not related by sequence, have been described. In the anaerobic bacterium Salmonella enterica they are encoded by the cobA gene (a housekeeping enzyme involved in both the de novo biosynthesis and the salvage of adenosylcobalamin), the pduO gene (involved in (S)-propane-1,2-diol utilization), and the eutT gene (involved in ethanolamine utilization). Since EutT hydrolyses triphosphate to diphosphate and phosphate during catalysis, it is classified as a separate enzyme. The mammalian enzyme belongs to the PduO type. The enzyme can act on other corrinoids, such as cob(II)inamide.

created 1972, modified 2004, modified 2018