VITAMIN B-12

General Function:

Zinc ion binding

Specific Function:

Catalyzes the transfer of a methyl group from methyl-cobalamin to homocysteine, yielding enzyme-bound cob(I)alamin and methionine. Subsequently, remethylates the cofactor using methyltetrahydrofolate (By similarity).

Gene Name:

MTR

Uniprot ID:

Q99707

Molecular Weight:

140525.91 Da

General Function:

Modified amino acid binding

Specific Function:

Involved in the degradation of several amino acids, odd-chain fatty acids and cholesterol via propionyl-CoA to the tricarboxylic acid cycle. MCM has different functions in other species.

Gene Name:

MUT

Uniprot ID:

P22033

Molecular Weight:

83133.755 Da

References

1. Moras E, Hosack A, Watkins D, Rosenblatt DS: Mitochondrial vitamin B12-binding proteins in patients with inborn errors of cobalamin metabolism. Mol Genet Metab. 2007 Feb;90(2):140-7. Epub 2006 Sep 29. [17011224 ]

General Function:

Oxidoreductase activity, oxidizing metal ions, nad or nadp as acceptor

Specific Function:

Involved in the reductive regeneration of cob(I)alamin (vitamin B12) cofactor required for the maintenance of methionine synthase in a functional state. Necessary for utilization of methylgroups from the folate cycle, thereby affecting transgenerational epigenetic inheritance. Folate pathway donates methyl groups necessary for cellular methylation and affects different pathways such as DNA methylation, possibly explaining the transgenerational epigenetic inheritance effects.

Gene Name:

MTRR

Uniprot ID:

Q9UBK8

Molecular Weight:

80409.22 Da

References

1. van der Linden IJ, den Heijer M, Afman LA, Gellekink H, Vermeulen SH, Kluijtmans LA, Blom HJ: The methionine synthase reductase 66A>G polymorphism is a maternal risk factor for spina bifida. J Mol Med (Berl). 2006 Dec;84(12):1047-54. Epub 2006 Oct 6. [17024475 ]

General Function:

Hydrolase activity

Specific Function:

Probable GTPase. May function as chaperone. May be involved in the transport of cobalamin (Cbl) into mitochondria for the final steps of adenosylcobalamin (AdoCbl) synthesis.

Gene Name:

MMAA

Uniprot ID:

Q8IVH4

Molecular Weight:

46537.865 Da

References

1. Dobson CM, Gradinger A, Longo N, Wu X, Leclerc D, Lerner-Ellis J, Lemieux M, Belair C, Watkins D, Rosenblatt DS, Gravel RA: Homozygous nonsense mutation in the MCEE gene and siRNA suppression of methylmalonyl-CoA epimerase expression: a novel cause of mild methylmalonic aciduria. Mol Genet Metab. 2006 Aug;88(4):327-33. Epub 2006 May 11. [16697227 ]

General Function:

Cobalamin binding

Specific Function:

May be involved in the binding and intracellular trafficking of cobalamin (vitamin B12).

Gene Name:

MMACHC

Uniprot ID:

Q9Y4U1

Molecular Weight:

31728.095 Da

References

1. Lerner-Ellis JP, Tirone JC, Pawelek PD, Dore 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: Identification of the gene responsible for methylmalonic aciduria and homocystinuria, cblC type. Nat Genet. 2006 Jan;38(1):93-100. Epub 2005 Nov 27. [16311595 ]

General Function:

Protein complex binding

Specific Function:

Catalyzes the conversion of 5,10-methylenetetrahydrofolate to 5-methyltetrahydrofolate, a co-substrate for homocysteine remethylation to methionine.

Gene Name:

MTHFR

Uniprot ID:

P42898

Molecular Weight:

74595.895 Da

References

1. Erdogan MO, Yildiz SH, Solak M, Eser O, Cosar E, Eser B, Koken R, Buyukbas S: C677T polymorphism of the methylenetetrahydrofolate reductase gene does not affect folic acid, vitamin B12, and homocysteine serum levels in Turkish children with neural tube defects. Genet Mol Res. 2010 Jun 22;9(2):1197-203. doi: 10.4238/vol9-2gmr816. [20589617 ]