Defective MTR does not transfer CH3 group from MTHF to cob(I)alamin

Stable Identifier
Reaction [transition]
Homo sapiens
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Methionine synthase (MTR) catalyses the transfer of a methyl group from 5-methyltetrahydrofolate (MTHF) to homocysteine (HCYS) to then form methionine (L-Met). In the first step, MTR mediates the transfer of a methyl group from 5-methyltetrahydrofolate (MTHF) to cob(I)alamin (B12s, bound to the enzyme MTR) to form the cofactor methylcobalamin (MeCbl), the form that activates MTR (Leclerc et al. 1996).

Defects in MTR cause methylcobalamin deficiency type G (cblG, methionine synthase deficiency; MIM:250940), an autosomal recessive inherited disease that causes mental retardation, macrocytic anemia, and homocystinuria. Mutations causing cblG include P1173L, Ile881, H920D, R585*, E1204* and A1204P (Leclerc et al. 1996, Gulati et al. 1996, Watkins et al. 2002).
Literature References
PubMed ID Title Journal Year
8968737 Human methionine synthase: cDNA cloning and identification of mutations in patients of the cblG complementation group of folate/cobalamin disorders

Ross, M, Adjalla, CE, Eydoux, P, Gravel, RA, Rosenblatt, DS, Christensen, B, Leclerc, D, Campeau, E, Rozen, R, Goyette, P

Hum Mol Genet 1996
12068375 Hyperhomocysteinemia due to methionine synthase deficiency, cblG: structure of the MTR gene, genotype diversity, and recognition of a common mutation, P1173L

Ge, B, Doré, C, Gravel, RA, Rosenblatt, DS, Kim, CD, Kim, W, Watkins, D, Philip, NS, Hudson, TJ, Murray, A, Hwang, HY, Shane, B, Hilton, JF, Ru, M, Wai, T, Wilson, A, Legakis, H, Hosack, A

Am. J. Hum. Genet. 2002
8968736 Defects in human methionine synthase in cblG patients

Banerjee, R, Baker, P, Gulati, S, Kruger, W, Brody, LC, Li, YN, Fowler, B

Hum. Mol. Genet. 1996
Normal reaction
Functional status

Loss of function of MTRR:mutant MTR(cob(I)alamin) [cytosol]

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