also known as MTR gene full mutation analysis in Blood or Tissue by Sequencing
The MTR gene encodes the methionine synthase (MS) enzyme. MS regenerates methionine from homocysteine using 5-MTHF as a methyl donor and vitamin B12 as the methyl transfer compound. In a first reaction, MS attaches the methyl group from 5-MTHF to vitamin B12, forming a MS-methylcobalamin complex. The MS-methylcobalamin complex then transfers this methyl group to the homocysteine, thus converting it into methionine. During this process, MS becomes oxidized over time and has to be reduced again to maintain proper function. This step is performed by methionine synthase reductase (MSR) which is encoded by the MTRR gene (see MTRR). MTR gene mutations, C3518T and A2756G, affect function of the enzyme even in the heterozygous form. They are associated with higher homocysteine levels and may lead to hypomethylation. Reported prevalence of A2756G in the Caucasian population is 1.7% in the homozygous form.