The role of Potassium in Cobalamin-Dependent Methionine Synthase
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The essential nutrient folate is used by the body to carry out reactions necessary for the production and maintenance of cells. If an enzyme that plays a role in the folate pathways of the body is not functioning to its full capacity due to a common mutation or polymorphism, an individual with this genetic defect may have an increased chance of developing a disease associated with folate deficiency, especially if they already have a low nutritional intake of folate. It is important to identify these polymorphisms, and to discover at what frequency they occur in the population. A major enzyme in the folate pathway is cobalamin-dependant methionine synthase (MetH). Recently it was discovered that the structure of MetH contains a potassium ion whose binding region is conserved in similar enzymes across different species levels. Because of this conservation, it was predicted that potassium is important for the function of MetH. If true, a genetic defect in the potassium binding would lead to the imbalance of folate metabolism, leaving individuals more at risk for disease. In this study, it was . shown that the presence of potassium is indeed needed for the full activity of MetH. In addition, the enzyme was found to be most active in concentrations of potassium similar to that found inside the cell, making these findings physiologically relevant. Finally, it was found that the specific component of the reaction in which potassium is likely to be involved is catalysis of the methyl transfer during the reaction.