Reaction: Defective MTR does not transfer CH3 group from MTHF to cob(I)alamin
- in pathway: Defective MTR causes HMAG
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).
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).
Reaction - small molecule participants:
5-methyl-THF [cytosol]
Reactome.org reaction link: R-HSA-3321918
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Reaction input - small molecules:
(6S)-5-methyltetrahydrofolate(2-)
Reaction output - small molecules:
Reactome.org link: R-HSA-3321918