The Enzyme Database

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Accepted name: cob(I)yrinic acid a,c-diamide adenosyltransferase
Reaction: (1) ATP + cob(I)yrinic acid a,c-diamide = triphosphate + adenosylcob(III)yrinic acid a,c-diamide
(2) ATP + cobinamide = triphosphate + adenosylcobinamide
For diagram of corrin biosynthesis (part 5), click here
Other name(s): CobA; CobO; ATP:corrinoid adenosyltransferase; cob(I)alamin adenosyltransferase; aquacob(I)alamin adenosyltransferase; aquocob(I)alamin vitamin B12s adenosyltransferase; ATP:cob(I)alamin Coβ-adenosyltransferase
Systematic name: ATP:cob(I)yrinic acid-a,c-diamide Coβ-adenosyltransferase
Comments: The corrinoid adenosylation pathway comprises three steps: (i) reduction of Co(III) to Co(II) by a one-electron transfer. This can be carried out by EC, aquacobalamin reductase or non-enzymically in the presence of dihydroflavin nucleotides [2]. (ii) Co(II) is reduced to Co(I) in a second single-electron transfer by EC, cob(II)alamin reductase and (iii) the Co(I) conducts a nucleophilic attack on the adenosyl moiety of ATP to leave the cobalt atom in a Co(III) state (EC The enzyme responsible for the adenosylation reaction is the product of the gene cobO in the aerobic bacterium Pseudomonas denitrificans and of the gene cobA in the anaerobic bacterium Salmonella typhimurium. In P. denitrificans, the enzyme shows specificity for cobyrinic acid a,c-diamide and the corrinoids that occur later in the biosynthetic pathway whereas CobA seems to have broader specificity [3]. While CobA has a preference for ATP and Mn2+, it is able to transfer a variety of nucleosides to the cobalt, including CTP, UTP and GTP, in decreasing order of preference [4] and to use Mg2+ instead of Mn2+.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 37277-84-2
1.  Vitols, E., Walker, G.A. and Huennekens, F.M. Enzymatic conversion of vitamin B12s to a cobamide coenzyme, α-(5,6-dimethylbenzimidazolyl)deoxyadenosylcobamide (adenosyl-B12). J. Biol. Chem. 241 (1966) 1455–1461. [PMID: 5946606]
2.  Bauer, C.B., Fonseca, M.V., Holden, H.M., Thoden, J.B., Thompson, T.B., Escalante-Semerena, J.C. and Rayment, I. Three-dimensional structure of ATP:corrinoid adenosyltransferase from Salmonella typhimurium in its free state, complexed with MgATP, or complexed with hydroxycobalamin and MgATP. Biochemistry 40 (2001) 361–374. [DOI] [PMID: 11148030]
3.  Fonseca, M.V. and Escalante-Semerena, J.C. An in vitro reducing system for the enzymic conversion of cobalamin to adenosylcobalamin. J. Biol. Chem. 276 (2001) 32101–32108. [DOI] [PMID: 11408479]
4.  Suh, S. and Escalante-Semerena, J.C. Purification and initial characterization of the ATP:corrinoid adenosyltransferase encoded by the cobA gene of Salmonella typhimurium. J. Bacteriol. 177 (1995) 921–925. [DOI] [PMID: 7860601]
[EC created 1972, modified 2004]

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