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UPB1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

UPB1 gene

The UPB1 gene provides instructions for making an enzyme responsible for the final step of breaking down pyrimidines, which are essential building blocks of DNA and RNA.

Normal Function

The UPB1 gene provides instructions for making an enzyme called beta-ureidopropionase. This enzyme is involved in the breakdown of molecules called pyrimidines, which are building blocks of DNA and its chemical cousin RNA.

The beta-ureidopropionase enzyme performs the last step of the process that breaks down pyrimidines. This step converts N-carbamyl-beta-aminoisobutyric acid to beta-aminoisobutyric acid and also breaks down N-carbamyl-beta-alanine to beta-alanine, ammonia, and carbon dioxide. Both beta-aminoisobutyric acid and beta-alanine are thought to play roles in the nervous system:

  • Beta-aminoisobutyric acid increases the production of a protein called leptin, which helps protect brain cells from damage caused by toxins and inflammation.
  • Beta-alanine is involved in sending signals between nerve cells (synaptic transmission) and in controlling the level of a chemical messenger called dopamine.

Health Conditions Related to Genetic Changes

Beta-ureidopropionase deficiency

At least 16 UPB1 gene mutations have been identified in people with beta-ureidopropionase deficiency. This disorder causes excessive amounts of N-carbamyl-beta-aminoisobutyric acid and N-carbamyl-beta-alanine to be released in the urine. Affected individuals may experience neurological problems, such as seizures and intellectual disability, ranging from mild to severe. Some individuals may have no neurological symptoms.

The mutations reduce or eliminate beta-ureidopropionase enzyme activity. Loss of this function reduces the production of beta-aminoisobutyric acid and beta-alanine, potentially impairing their functions in the nervous system. The severity of the condition may depend on the extent of the reduction in enzyme activity and other genetic or environmental factors.

Other Names for This Gene

  • beta-alanine synthase
  • beta-ureidopropionase
  • BUP1
  • n-carbamoyl-beta-alanine amidohydrolase
  • ureidopropionase, beta

Frequently Asked Questions

Diagnosis relies on a combination of biochemical and genetic testing. First, a urine organic acid analysis (often by gas chromatography‑mass spectrometry) will show markedly elevated N‑carbamyl‑beta‑aminoisobutyric acid and N‑carbamyl‑beta‑alanine. If these metabolites are present, sequencing of the UPB1 gene (either targeted panel or whole‑exome sequencing) confirms pathogenic variants.
There is no cure, but management focuses on reducing neurotoxic metabolite buildup and supporting neurologic function. Some clinicians trial a low‑purine, low‑pyrimidine diet to lessen substrate load, although evidence is limited. Supplementation with beta‑alanine or beta‑aminoisobutyric acid is experimental and should only be done under metabolic specialist supervision. Seizure control with standard antiepileptic drugs and early developmental therapy (physical, occupational, speech) are essential.
cute neurological changes such as new‑onset seizures, sudden loss of consciousness, or rapid worsening of developmental regression should prompt immediate evaluation. Because metabolic crises can be triggered by illness or fasting, any fever, vomiting, or prolonged poor intake warrants urgent contact with a metabolic specialist or emergency department.
Yes. UPB1 deficiency follows an autosomal‑recessive inheritance pattern, so each parent is typically a carrier. Testing siblings with targeted mutation analysis is recommended, especially if they show any developmental concerns or unexplained seizures. Carrier testing for parents can also inform future family planning.
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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