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

MMUT gene

The MMUT gene provides instructions for creating an enzyme essential for breaking down specific amino acids, fats, and cholesterol.

Normal Function

The MMUT gene provides instructions for making an enzyme called methylmalonyl CoA mutase. This enzyme is active in mitochondria, the energy-producing centers within cells.

Methylmalonyl CoA mutase is responsible for a specific step in the breakdown of several protein building blocks (amino acids), specifically isoleucine, methionine, threonine, and valine. The enzyme also assists in breaking down certain types of fats (lipids) and cholesterol. The process involves several chemical reactions that convert these substances into a molecule called methylmalonyl CoA. Working with a compound called adenosylcobalamin (AdoCbl)—a form of vitamin B12—the enzyme converts methylmalonyl CoA into succinyl-CoA, which is subsequently used for energy.

Health Conditions Related to Genetic Changes

Methylmalonic acidemia

More than 200 mutations in the MMUT gene have been identified in individuals with methylmalonic acidemia, a condition characterized by feeding difficulties, developmental delay, and long-term health complications. These genetic changes prevent the production of functional methylmalonyl CoA mutase or reduce its activity, leading to the improper breakdown of proteins and lipids. This defect causes toxic compounds, including methylmalonyl CoA, to accumulate in the body's organs and tissues.

  • mut0 form: Mutations that prevent the production of any functional enzyme lead to this form, which is the most severe with the poorest outcome.
  • mut- form: Mutations that alter the enzyme's structure but do not completely eliminate its activity lead to this form, which is typically less severe with more variable symptoms.

Other Names for This Gene

  • MCM
  • methylalonyl-CoA mutase
  • methylamlony-CoA isomerase
  • methylmalonyl CoA mutase
  • methylmalonyl Coenzyme A mutase
  • methylmalonyl Coenzyme A mutase precursor
  • MUT
  • MUTA_HUMAN

Genomic Location

The MMUT gene is found on chromosome 6.

Frequently Asked Questions

low‑protein diet that limits isoleucine, methionine, threonine, and valine can reduce the buildup of toxic metabolites. Some patients also benefit from a low‑fat, low‑cholesterol diet and supplementation with L‑carnitine to help remove excess fatty acids. A registered dietitian experienced in metabolic disorders should tailor the plan.
Infants with MMUT mutations often show poor feeding, vomiting, lethargy, and a distinctive “sweet” or “fruity” breath odor. They may also have developmental delays or seizures within the first few weeks of life. Early recognition and evaluation by a metabolic specialist are critical.
blood test measuring methylmalonic acid levels and a urine organic acid profile are the first steps. If elevated, a genetic test of the MMUT gene is performed to identify the specific mutation. Confirmation guides treatment and family counseling.
High‑dose hydroxocobalamin (a form of vitamin B12) is often given intramuscularly or orally. It serves as a cofactor for the enzyme, improving its activity in many patients, especially those with residual enzyme function. Regular monitoring of methylmalonic acid levels determines response.
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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