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Methionine Adenosyltransferase 1A (MAT1A) is an enzyme which controls the production of S-adenosylmethionine (SAM) which functions as a methyl donor in the body, it is encoded for by the MAT1A gene.

SAM is a methyl donor in the body involved in numerous processes including DNA methylation to regulate gene expression, transsulfuration to convert homocysteine to cysteine and remove sulfur from the body and various other processes. It is formed by MAT1A which uses combines the essential amino acid methionine with a molecule of ATP and water 1. As such MAT1A forms a key part of the methionine cycle which interacts with the one carbon pathway into a larger network which is sometimes termed the methylation cycle.

Therefore, MAT1A is sensitive to alterations in other parts of the network; for example SNPs associated with reduced methylenetetrahydrofolate reductase (MTHFR) function can lead to reductions in the levels of methionine present which then limits the formation of SAM, inhibiting numerous cellular processes.


Science Grade
Gastrointestinal Health
rsID Number Major Allele Minor Allele Minor Allele Frequency (%) Major Amino Acid Minor Amino Acid
rs72558181 g a 0.1 Arg His

Risk Description

The risk ‘A’ allele of G791A in the MAT1A gene results in a loss of MAT1A function leading to the development of hypermethioninemia, or an excess of methionine in the blood, which is also associated with a reduction in the amount of SAM available to act as a methyl donor 24. The occurrence of the ‘A’ allele in the population is very low which has limited investigation into its effects.

Symptoms are very severe in those carrying two copies of the ‘A’ can be very severe and can include severe neurological issues 24. It is unclear what impact carrying a single risk ‘A’ allele has, in part due to its rarity in the population.

Direct Nutrients:*

Ingredient Active Ingredient Effect

Potassium is one of two cofactors for MAT1A, required for it to function correctly 5. In those carrying one risk ‘A’ allele of G791A supplementation may ensure that MAT1A is working optimally, potentially limiting the accumulation of methionine.


Magnesium is one of two cofactors for MAT1A which it requires in order to function properly 5. In those carrying one risk ‘A’ allele of G791A supplementation with magnesium may ensure that MAT1A activity is working correctly, limiting the accumulation of methionine and providing sufficient SAM.

Indirect Nutrients:*

Ingredient Active Ingredient Effect

SAM is produced by MAT1A by combining a methionine molecule with water and ATP; and is required for numerous reactions throughout the body as a methyl donor 6. In those carrying one copy of the risk ‘A’ allele of G791A, which may be associated with a reduction in SAM levels, will ensure that it is not limiting in the body.

Nutritional Contraindications:*

Ingredient Active Ingredient Effect

The risk ‘A’ allele of G791A is associated with an accumulation of methionine when two copies are present. It is unclear what effect a single copy of the risk ‘A’ allele has on methionine levels, and due to its important role removal of methionine from the diet is not to be recommended on the basis of a genetic test alone. However, a simple blood test can determine methionine levels and be used to influence diet 7.

Discuss this information with your doctor before taking any course of action.


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