| Entry |
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| Name |
cyanocobalamin reductase (cyanide-eliminating);
MMACHC (gene name);
CblC;
cyanocobalamin reductase;
cyanocobalamin reductase (NADPH, cyanide-eliminating);
cyanocobalamin reductase (NADPH, CN-eliminating);
NADPH:cyanocob(III)alamin oxidoreductase (cyanide-eliminating);
cob(I)alamin, cyanide:NADP+ oxidoreductase
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| Class |
Oxidoreductases;
Oxidizing metal ions;
With NAD+ or NADP+ as acceptor
 |
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| Sysname |
cob(II)alamin, hydrogen cyanide:NADP+ oxidoreductase
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| Reaction(IUBMB) |
2 cob(II)alamin-[cyanocobalamin reductase] + 2 hydrogen cyanide + NADP+ = 2 cyanocob(III)alamin + 2 [cyanocobalamin reductase] + NADPH + H+ [RN: R02999]
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| Reaction(KEGG) |
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| Substrate |
cob(II)alamin-[cyanocobalamin reductase];
hydrogen cyanide [CPD: C01326];
NADP+ [CPD: C00006]
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| Product |
cyanocob(III)alamin [CPD: C02823];
[cyanocobalamin reductase];
NADPH [CPD: C00005];
H+ [CPD: C00080]
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| Comment |
The mammalian enzyme, which is cytosolic, can bind internalized cyanocobalamin and process it to cob(II)alamin by removing the upper axial ligand. The product remains bound to the protein, which, together with its interacting partner MMADHC, transfers it directly to downstream enzymes involved in adenosylcobalamin and methylcobalamin biosynthesis. In addition to its decyanase function, the mammalian enzyme also catalyses an entirely different chemical reaction with alkylcobalamins, using the thiolate of glutathione for nucleophilic displacement, generating cob(I)alamin and the corresponding glutathione thioether (cf. EC 2.5.1.151, alkylcobalamin dealkylase).
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| History |
EC 1.16.1.6 created 1989 as EC 1.6.99.12, transferred 2002 to EC 1.16.1.6, modified 2018
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| Pathway |
| ec00860 | Porphyrin and chlorophyll metabolism |
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| Orthology |
| K14618 | cyanocobalamin reductase (cyanide-eliminating) / alkylcobalamin dealkylase |
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| Genes |
» show all
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| Reference |
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| Authors |
Watanabe F, Oki Y, Nakano Y, Kitaoka S. |
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| Title |
Occurrence and characterization of cyanocobalamin reductase (NADPH; CN-eliminating) involved in decyanation of cyanocobalamin in Euglena gracilis. |
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| Journal |
J Nutr Sci Vitaminol (Tokyo) 34:1-10 (1988) |
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| Reference |
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| Authors |
Kim J, Gherasim C, Banerjee R |
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| Title |
Decyanation of vitamin B12 by a trafficking chaperone. |
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| Journal |
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| Reference |
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| Authors |
Koutmos M, Gherasim C, Smith JL, Banerjee R |
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| Title |
Structural basis of multifunctionality in a vitamin B12-processing enzyme. |
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| Journal |
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| Reference |
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| Authors |
Mah W, Deme JC, Watkins D, Fung S, Janer A, Shoubridge EA, Rosenblatt DS, Coulton JW |
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| Title |
Subcellular location of MMACHC and MMADHC, two human proteins central to intracellular vitamin B(12) metabolism. |
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| Journal |
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| Other DBs |
| ExplorEnz - The Enzyme Database: | 1.16.1.6 |
| ExPASy - ENZYME nomenclature database: | 1.16.1.6 |
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