Accepted name: adenosylcobinamide kinase
Reaction: RTP + adenosylcobinamide = adenosylcobinamide phosphate + RDP
where RTP is either ATP or GTP (for symbol definitions, click here)
For diagram of reaction click here.
Other name(s): CobU; adenosylcobinamide kinase/adenosylcobinamide-phosphate guanylyltransferase; AdoCbi kinase/AdoCbi-phosphate guanylyltransferase
Systematic name: RTP:adenosylcobinamide phosphotransferase
Comments: In Salmonella typhimurium LT2, under anaerobic conditions, CobU (EC 18.104.22.168 and EC 22.214.171.124), CobT (EC 126.96.36.199), CobC (EC 188.8.131.52) and CobS (EC 184.108.40.206) catalyse rea>actions in the nucleotide loop assembly pathway, which convert adenosylcobinamide (AdoCbi) into adenosylcobalamin (AdoCbl). CobT and CobC are involved in 5,6-dimethylbenzimidazole activation whereby 5,6-dimethylbenzimidazole is converted to its riboside, α-ribazole. The second branch of the nucleotide loop assembly pathway is the cobinamide (Cbi) activation branch where AdoCbi or adenosylcobinamide-phosphate is converted to the activated intermediate AdoCbi-GDP by Cob U. The final step in adenosylcobalamin biosynthesis is the condensation of AdoCbi-GDP with α-ribazole, which is catalysed by EC 220.127.116.11, adenosylcobinamide-GDP ribazoletransferase (CobS), to yield adenosylcobalamin. CobU is a bifunctional enzyme that has both kinase (EC 18.104.22.168) and guanylyltransferase (EC 22.214.171.124, adenosylcobinamide-phosphate guanylyltransferase) activities. However, both activities are not required at all times. The kinase activity has been proposed to function only when S. typhimurium is assimilating cobinamide whereas the guanylyltransferase activity is required for both assimilation of exogenous cobinamide and for de novo synthesis of adenosylcobalamin .
Links to other databases: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number: 169592-51-2
1. O'Toole, G.A. and Escalante-Semerena, J.C. Purification and characterization of the bifunctional CobU enzyme of Salmonella typhimurium LT2. Evidence for a CobU-GMP intermediate. J. Biol. Chem. 270 (1995) 23560-23569. [PMID: 7559521]
2. Thompson, T.B., Thomas, M.G., Escalante-Semerena, J.C. and Rayment, I. Three-dimensional structure of adenosylcobinamide kinase/adenosylcobinamide phosphate guanylyltransferase from Salmonella typhimurium determined to 2.3 Å resolution. Biochemistry 37 (1998) 7686-7695. [PMID: 9601028]
3. Thompson, T.B., Thomas, M.G., Escalante-Semerena, J.C. and Rayment, I. Three-dimensional structure of adenosylcobinamide kinase/adenosylcobinamide phosphate guanylyltransferase (CobU) complexed with GMP: evidence for a substrate-induced transferase active site. Biochemistry 38 (1999) 12995-13005. [PMID: 10529169]
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