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GNMT gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

GNMT gene

The GNMT gene produces an enzyme that regulates methionine metabolism and plays a role in controlling gene expression through methylation.

Normal Function

The GNMT gene provides instructions for producing the enzyme glycine N-methyltransferase. This enzyme is involved in a multistep process that breaks down the protein building block (amino acid) methionine. Specifically, glycine N-methyltransferase starts a reaction that converts glycine and S-adenosylmethionine (AdoMet) to N-methylglycine and S-adenosylhomocysteine (AdoHcy).

This reaction helps control the ratio of AdoMet to AdoHcy, which is vital for methylation—the addition of methyl groups to DNA, proteins, and lipids. Methylation regulates gene activity, protein and lipid reactions, and the processing of neurotransmitters. Additionally, this enzyme is involved in processing toxic compounds in the liver.

Health Conditions Related to Genetic Changes

Hypermethioninemia

Variants in the GNMT gene can lead to hypermethioninemia, characterized by an excess of methionine in the blood. These variants reduce the function of the glycine N-methyltransferase enzyme, impairing the breakdown of methionine. This buildup can result in neurological problems in some individuals.

Cancers

Inherited and acquired (somatic) variations in the GNMT gene have been associated with an increased risk of liver and prostate cancers. These variants likely impair the enzyme's ability to process cancer-causing substances and regulate genes responsible for controlling cell growth. When regulation fails, cells may grow uncontrollably, leading to tumor formation.

Other Names for This Gene

  • Glycine Methyltransferase
  • Glycine Sarcosine Methyltransferase
  • Glycine Sarcosine N-Methyltransferase
  • GNMT_HUMAN

Frequently Asked Questions

Yes, hypermethioninemia due to GNMT mutations is typically inherited in an autosomal recessive pattern. This means a person must inherit two altered copies of the gene, one from each parent, to develop the condition. Parents who carry one copy of the variant are usually healthy and do not show symptoms but have a 25% chance with each pregnancy of having a child with the disorder. Genetic counseling can help families understand these probabilities and discuss testing options for at-risk relatives.
GNMT variants are associated with an increased risk of liver and prostate cancers, likely because the enzyme is less effective at processing toxic compounds and regulating cell growth genes. While there is no single standardized screening protocol exclusively for GNMT carriers, clinicians may recommend enhanced surveillance, such as regular liver imaging or prostate-specific antigen (PSA) testing, depending on the specific variant and family history. Patients should discuss personalized risk assessment with their oncologist or genetic counselor to determine the appropriate monitoring schedule.
Early signs often involve neurological and developmental issues, such as delayed motor milestones, intellectual disability, or seizures. In some cases, individuals may present with behavioral problems or learning difficulties. Because the buildup of methionine can affect the brain, parents or caregivers might notice that a child is not meeting standard developmental benchmarks, which prompts medical evaluation and blood testing for elevated methionine levels.
Dietary management is a key part of treatment, typically involving a low-methionine diet to reduce the substrate that the impaired enzyme cannot break down. This often means limiting high-protein foods, particularly those rich in methionine like meat, fish, and eggs. However, strict restriction must be balanced against the need for adequate nutrition, especially in children. Patients should work with a metabolic dietitian to create a safe plan, as excessive restriction can lead to protein deficiency. Supplements are generally not a substitute for dietary control and should only be used under medical supervision.
Source: MedlinePlus, National Library of Medicine

MedlinePlus brings together authoritative health information from the National Library of Medicine (NLM), the National Institutes of Health (NIH), and other government agencies and health-related organizations.

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