The Enzyme Database

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EC 1.3.1.54     
Accepted name: precorrin-6A reductase
Reaction: precorrin-6B + NADP+ = precorrin-6A + NADPH + H+
For diagram of corrin biosynthesis (part 3), click here
Other name(s): precorrin-6X reductase; precorrin-6Y:NADP+ oxidoreductase; CobK
Systematic name: precorrin-6B:NADP+ oxidoreductase
Comments: The enzyme, which participates in the aerobic (late cobalt insertion) pathway of adenosylcobalamin biosynthesis, catalyses the reduction of the double bond between C-18 and C-19 of precorrin-6A. See EC 1.3.1.106, cobalt-precorrin-6A reductase, for the corresponding enzyme that participates in the anaerobic cobalamin biosynthesis pathway.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 137573-72-9
References:
1.  Blanche, F., Thibaut, D., Famechon, A., Debussche, L., Cameron, B. and Crouzet, J. Precorrin-6X reductase from Pseudomonas denitrificans: purification and characterization of the enzyme and identification of the structural gene. J. Bacteriol. 174 (1992) 1036–1042. [DOI] [PMID: 1732193]
2.  Warren, M.J., Raux, E., Schubert, H.L. and Escalante-Semerena, J.C. The biosynthesis of adenosylcobalamin (vitamin B12). Nat. Prod. Rep. 19 (2002) 390–412. [PMID: 12195810]
[EC 1.3.1.54 created 1999, modified 2004]
 
 
EC 1.3.1.106     
Accepted name: cobalt-precorrin-6A reductase
Reaction: cobalt-precorrin-6B + NAD+ = cobalt-precorrin-6A + NADH + H+
For diagram of anaerobic corrin biosynthesis (part 2), click here
Other name(s): cbiJ (gene name)
Systematic name: cobalt-precorrin-6B:NAD+ oxidoreductase
Comments: The enzyme, which participates in the anaerobic (early cobalt insertion) pathway of adenosylcobalamin biosynthesis, catalyses the reduction of the double bond between C-18 and C-19 of cobalt-precorrin-6A. The enzyme from the bacterium Bacillus megaterium has no activity with NADPH. See EC 1.3.1.54, precorrin-6A reductase, for the corresponding enzyme that participates in the aerobic cobalamin biosynthesis pathway.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Kim, W., Major, T.A. and Whitman, W.B. Role of the precorrin 6-X reductase gene in cobamide biosynthesis in Methanococcus maripaludis. Archaea 1 (2005) 375–384. [PMID: 16243778]
2.  Moore, S.J., Lawrence, A.D., Biedendieck, R., Deery, E., Frank, S., Howard, M.J., Rigby, S.E. and Warren, M.J. Elucidation of the anaerobic pathway for the corrin component of cobalamin (vitamin B12). Proc. Natl. Acad. Sci. USA 110 (2013) 14906–14911. [DOI] [PMID: 23922391]
[EC 1.3.1.106 created 2014]
 
 
EC 2.1.1.132     
Accepted name: precorrin-6B C5,15-methyltransferase (decarboxylating)
Reaction: 2 S-adenosyl-L-methionine + precorrin-6B = 2 S-adenosyl-L-homocysteine + precorrin-8X + CO2 (overall reaction)
(1a) S-adenosyl-L-methionine + precorrin-6B = S-adenosyl-L-homocysteine + precorrin-7 + CO2
(1b) S-adenosyl-L-methionine + precorrin-7 = S-adenosyl-L-homocysteine + precorrin-8X
For diagram of corrin biosynthesis (part 4), click here
Glossary: precorrin-6B = precorrin-6Y
Other name(s): precorrin-6 methyltransferase; precorrin-6Y methylase; precorrin-6Y C5,15-methyltransferase (decarboxylating); cobL (gene name)
Systematic name: S-adenosyl-L-methionine:1-precorrin-6B C5,15-methyltransferase (C-12-decarboxylating)
Comments: The enzyme participates in the aerobic (late cobalt insertion) adenosylcobalamin biosynthesis pathway. The enzyme from the bacterium Pseudomonas denitrificans is a fusion protein with two active sites; one catalyses the methylation at C-15 followed by decarboxylation of the C-12 acetate side chain, while the other catalyses the methylation at C-5. The corresponding activities in the anaerobic adenosylcobalamin biosynthesis pathway are catalysed by EC 2.1.1.196, cobalt-precorrin-6B (C15)-methyltransferase [decarboxylating], and EC 2.1.1.289, cobalt-precorrin-7 (C5)-methyltransferase, respectively.
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB, CAS registry number: 162995-22-4
References:
1.  Blanche, F., Famechon, A., Thibaut, D., Debussche, L., Cameron, B., Crouzet, J. Biosynthesis of vitamin B12 in Pseudomonas denitrificans: the biosynthetic sequence from precorrin-6Y to precorrin-8X is catalyzed by the cobL gene product. J. Bacteriol. 174 (1992) 1050–1052. [DOI] [PMID: 1732195]
2.  Deery, E., Schroeder, S., Lawrence, A.D., Taylor, S.L., Seyedarabi, A., Waterman, J., Wilson, K.S., Brown, D., Geeves, M.A., Howard, M.J., Pickersgill, R.W. and Warren, M.J. An enzyme-trap approach allows isolation of intermediates in cobalamin biosynthesis. Nat. Chem. Biol. 8 (2012) 933–940. [DOI] [PMID: 23042036]
[EC 2.1.1.132 created 1999, modified 2013]
 
 
EC 2.1.1.196     
Accepted name: cobalt-precorrin-6B (C15)-methyltransferase [decarboxylating]
Reaction: S-adenosyl-L-methionine + cobalt-precorrin-6B = S-adenosyl-L-homocysteine + cobalt-precorrin-7 + CO2
For diagram of anaerobic corrin biosynthesis (part 2), click here
Other name(s): cbiT (gene name); S-adenosyl-L-methionine:precorrin-7 C15-methyltransferase (C-12-decarboxylating); cobalt-precorrin-7 (C15)-methyltransferase [decarboxylating]
Systematic name: S-adenosyl-L-methionine:precorrin-6B C15-methyltransferase (C-12-decarboxylating)
Comments: This enzyme, which participates in the anaerobic (early cobalt insertion) adenosylcobalamin biosynthesis pathway, catalyses both methylation at C-15 and decarboxylation of the C-12 acetate side chain of cobalt-precorrin-6B. The equivalent activity in the aerobic adenosylcobalamin biosynthesis pathway is catalysed by the bifunctional enzyme EC 2.1.1.132, precorrin-6B C5,15-methyltransferase (decarboxylating).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc, PDB
References:
1.  Keller, J.P., Smith, P.M., Benach, J., Christendat, D., deTitta, G.T. and Hunt, J.F. The crystal structure of MT0146/CbiT suggests that the putative precorrin-8w decarboxylase is a methyltransferase. Structure 10 (2002) 1475–1487. [DOI] [PMID: 12429089]
2.  Santander, P.J., Kajiwara, Y., Williams, H.J. and Scott, A.I. Structural characterization of novel cobalt corrinoids synthesized by enzymes of the vitamin B12 anaerobic pathway. Bioorg. Med. Chem. 14 (2006) 724–731. [DOI] [PMID: 16198574]
3.  Moore, S.J., Lawrence, A.D., Biedendieck, R., Deery, E., Frank, S., Howard, M.J., Rigby, S.E. and Warren, M.J. Elucidation of the anaerobic pathway for the corrin component of cobalamin (vitamin B12). Proc. Natl. Acad. Sci. USA 110 (2013) 14906–14911. [DOI] [PMID: 23922391]
[EC 2.1.1.196 created 2010, modified 2013]
 
 
EC 2.1.1.289     
Accepted name: cobalt-precorrin-7 (C5)-methyltransferase
Reaction: S-adenosyl-L-methionine + cobalt-precorrin-7 = S-adenosyl-L-homocysteine + cobalt-precorrin-8
For diagram of anaerobic corrin biosynthesis (part 2), click here
Other name(s): CbiE
Systematic name: S-adenosyl-L-methionine:precorrin-7 C5-methyltransferase
Comments: This enzyme catalyses the methylation at C-5 of cobalt-precorrin-7, a step in the anaerobic (early cobalt insertion) adenosylcobalamin biosynthesis pathway. The equivalent activity in the aerobic adenosylcobalamin biosynthesis pathway is catalysed by the bifunctional enzyme EC 2.1.1.132, precorrin-6B C5,15-methyltransferase (decarboxylating).
Links to other databases: BRENDA, EXPASY, KEGG, MetaCyc
References:
1.  Santander, P.J., Kajiwara, Y., Williams, H.J. and Scott, A.I. Structural characterization of novel cobalt corrinoids synthesized by enzymes of the vitamin B12 anaerobic pathway. Bioorg. Med. Chem. 14 (2006) 724–731. [DOI] [PMID: 16198574]
2.  Moore, S.J., Lawrence, A.D., Biedendieck, R., Deery, E., Frank, S., Howard, M.J., Rigby, S.E. and Warren, M.J. Elucidation of the anaerobic pathway for the corrin component of cobalamin (vitamin B12). Proc. Natl. Acad. Sci. USA 110 (2013) 14906–14911. [DOI] [PMID: 23922391]
[EC 2.1.1.289 created 2010]
 
 


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