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Available structures
PDBOrtholog search: PDBe RCSB
AliasesMMACHC, cblC, methylmalonic aciduria (cobalamin deficiency) cblC type, with homocystinuria, metabolism of cobalamin associated C
External IDsOMIM: 609831 MGI: 1914346 HomoloGene: 12082 GeneCards: MMACHC
RefSeq (mRNA)



RefSeq (protein)



Location (UCSC)Chr 1: 45.5 – 45.51 MbChr 4: 116.7 – 116.71 Mb
PubMed search[3][4]
View/Edit HumanView/Edit Mouse

Methylmalonic aciduria and homocystinuria type C protein (MMACHC) is a protein that in humans is encoded by the MMACHC gene.[5]


The C-terminal region of the product of the MMACHC gene is similar to TonB, a bacterial protein involved in energy transduction for cobalamin uptake.[5] The MMACHC gene product catalyzes the decyanation of cyanocobalamin as well as the dealkylation of alkylcobalamins including methylcobalamin and adenosylcobalamin.[6] This function has also been attributed to cobalamin reductases.[7] The MMACHC gene product and cobalamin reductases enable the interconversion of cyano- and alkylcobalamins.[8][9]

Clinical significance

Mutations are associated with methylmalonic acidemia.[5][10][11][12]


  1. ^ a b c GRCh38: Ensembl release 89: ENSG00000132763 - Ensembl, May 2017
  2. ^ a b c GRCm38: Ensembl release 89: ENSMUSG00000028690 - Ensembl, May 2017
  3. ^ "Human PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  4. ^ "Mouse PubMed Reference:". National Center for Biotechnology Information, U.S. National Library of Medicine.
  5. ^ a b c Lerner-Ellis JP, Tirone JC, Pawelek PD, Doré C, Atkinson JL, Watkins D, Morel CF, Fujiwara TM, Moras E, Hosack AR, Dunbar GV, Antonicka H, Forgetta V, Dobson CM, Leclerc D, Gravel RA, Shoubridge EA, Coulton JW, Lepage P, Rommens JM, Morgan K, Rosenblatt DS (January 2006). "Identification of the gene responsible for methylmalonic aciduria and homocystinuria, cblC type". Nat. Genet. 38 (1): 93–100. doi:10.1038/ng1683. PMID 16311595. S2CID 7688576.
  6. ^ Luciana Hannibal, Jihoe Kim, Nicola E. Brasch, Sihe Wang, David S. Rosenblatt, Ruma Banerjee, and Donald W. Jacobsen (August 2009). "Processing of alkylcobalamins in mammalian cells: a role for the MMACHC (cblC) gene product". Mol Genet Metab. 2009 Aug; 97(4): 260–266.
  7. ^ Watanabe F, Nakano Y. "Purification and characterization of aquacobalamin reductases from mammals". Methods Enzymol. 1997;281;295-305.
  8. ^ Quadros EV, Jackson B, Hoffbrand AV, Linnell JC. "Interconversion of cobalamins in human lymphocytes in vitro and the influence of nitrous oxide on the synthesis of cobalamin coenzymes". Vitamin B12, Proceedings of the Third European Symposium on Vitamin B12 and Intrinsic Factor. 1979;1045-1054.
  9. ^ Quadros, EV. "Advances in the Understanding of Cobalamin Assimilation and Metabolism". Br J Haematol. 2010 Jan; 148(2): 195–204.
  10. ^ Ben-Omran TI, Wong H, Blaser S, Feigenbaum A (May 2007). "Late-onset cobalamin-C disorder: a challenging diagnosis". Am. J. Med. Genet. A. 143A (9): 979–84. doi:10.1002/ajmg.a.31671. PMID 17431913. S2CID 19791175.
  11. ^ Morel CF, Lerner-Ellis JP, Rosenblatt DS (August 2006). "Combined methylmalonic aciduria and homocystinuria (cblC): phenotype-genotype correlations and ethnic-specific observations". Mol. Genet. Metab. 88 (4): 315–21. doi:10.1016/j.ymgme.2006.04.001. PMID 16714133.
  12. ^ Tsai AC, Morel CF, Scharer G, Yang M, Lerner-Ellis JP, Rosenblatt DS, Thomas JA (October 2007). "Late-onset combined homocystinuria and methylmalonic aciduria (cblC) and neuropsychiatric disturbance". Am. J. Med. Genet. A. 143A (20): 2430–4. doi:10.1002/ajmg.a.31932. PMID 17853453. S2CID 19372503.

Further reading

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