metioninsyntházy

Methionine synthase, also known as MS or MTR, is an enzyme that plays a crucial role in the human body's metabolism. It catalyzes the transfer of a methyl group from 5-methyltetrahydrofolate (5-MTHF) to homocysteine, thereby regenerating methionine. This process is essential for a variety of cellular functions, including protein synthesis and DNA methylation.

Methionine synthase is a cobalamin-dependent enzyme, meaning it requires vitamin B12 (cobalamin) as a cofactor to function. The vitamin B12 binds to the enzyme and facilitates the methyl transfer. Without sufficient vitamin B12, methionine synthase activity can be impaired, leading to a buildup of homocysteine in the blood, a condition known as hyperhomocysteinemia. High levels of homocysteine are associated with an increased risk of cardiovascular disease and neural tube defects in developing fetuses.

The enzyme also relies on folate, specifically 5-MTHF, as the methyl donor. Folate is a B vitamin that is vital for cell growth and division. Deficiencies in folate can also impact methionine synthase activity, further contributing to elevated homocysteine levels.

In addition to its role in methionine synthesis, the methionine synthase reaction is also important for the folate cycle. The regeneration of tetrahydrofolate from 5-MTHF ensures a continuous supply of this essential cofactor for other folate-dependent enzymes involved in nucleotide synthesis and amino acid metabolism. Therefore, methionine synthase is a central hub in the interconnected pathways of one-carbon metabolism.