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EC 1.16.1.6 Details
EC number
1.16.1.6
Accepted name
cyanocobalamin reductase
Reaction
2 cob(II)alamin-[cyanocobalamin reductase] + 2 hydrogen cyanide + NADP+ = 2 cyanocob(III)alamin + 2 [cyanocobalamin reductase] + NADPH + H+
Other name(s)
MMACHC (gene name), CblC, cyanocobalamin reductase (NADPH, cyanide-eliminating), cyanocobalamin reductase (NADPH, CN-eliminating), NADPH:cyanocob(III)alamin oxidoreductase (cyanide-eliminating), cob(I)alamin, cyanide:NADP+ oxidoreductase, cyanocobalamin reductase (cyanide-eliminating)
Systematic name
cob(II)alamin, hydrogen cyanide:NADP+ oxidoreductase
CAS registry number
131145-00-1
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).
History
created 1989 as EC 1.6.99.12, transferred 2002 to EC 1.16.1.6, modified 2018, modified 2021
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