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

PCCB gene

The PCCB gene provides instructions for creating the beta subunit of the propionyl-CoA carboxylase enzyme, which is vital for processing proteins and fats.

Normal Function

The PCCB gene provides instructions for making part of an enzyme called propionyl-CoA carboxylase, specifically, the beta subunit of this enzyme. Six beta subunits come together with six alpha subunits (produced from the PCCA gene) to form a functioning enzyme.

Propionyl-CoA carboxylase plays a role in the normal processing of proteins. It carries out a particular step in the breakdown of several protein building blocks (amino acids) called isoleucine, methionine, threonine, and valine. Propionyl-CoA carboxylase also helps break down certain types of lipids (fats) and cholesterol. First, several chemical reactions convert the amino acids, lipids, or cholesterol to a molecule called propionyl-CoA. Using the B vitamin biotin, propionyl-CoA carboxylase then converts propionyl-CoA to a molecule called methylmalonyl-CoA. Additional enzymes break down methylmalonyl-CoA into other molecules that are used for energy.

Health Conditions Related to Genetic Changes

Propionic acidemia

More than 100 mutations in the PCCB gene have been identified in people with propionic acidemia, a condition that causes severe health problems appearing shortly after birth. These mutations include changes in single DNA building blocks (nucleotides) and insertions or deletions of genetic material in the PCCB gene. PCCB mutations prevent the production of functional propionyl-CoA carboxylase or reduce the enzyme's activity. The altered or missing enzyme prevents certain parts of proteins and lipids from being broken down properly. As a result, propionyl-CoA and other potentially toxic compounds can build up to toxic levels in the body. This buildup damages the brain and nervous system, causing the serious health problems associated with propionic acidemia.

Other Names for This Gene

  • PCCase beta subunit
  • PCCB_HUMAN
  • propanoyl-CoA:carbon dioxide ligase beta subunit
  • propionyl CoA carboxylase, beta polypeptide
  • propionyl-CoA carboxylase beta subunit
  • propionyl-CoA carboxylase, beta subunit

Frequently Asked Questions

Biotin is a B vitamin that acts as a cofactor for the propionyl-CoA carboxylase enzyme. In propionic acidemia, the enzyme is defective or missing due to PCCB mutations, so while biotin is essential for the enzyme to function, supplementing it does not fix the underlying genetic defect or cure the disease. However, high-dose biotin supplementation is often part of the standard management protocol because it may help maximize the residual activity of any partially functional enzyme remaining in the body, potentially improving metabolic stability.
Early signs often appear within the first few days to weeks of life and include poor feeding, vomiting, lethargy, and hypotonia (low muscle tone). As the condition progresses, infants may develop seizures, metabolic acidosis, and elevated ammonia levels. Because the buildup of toxic metabolites can cause rapid and severe brain damage, immediate medical intervention is critical. Treatment typically involves hospitalization for stabilization, followed by a strict lifelong dietary management plan to prevent metabolic crises.
The diet is designed to limit the intake of amino acids that break down into propionyl-CoA. Patients must strictly avoid or severely restrict foods high in isoleucine, methionine, threonine, and valine. This typically means avoiding most animal proteins such as meat, fish, eggs, and dairy, as well as certain grains and legumes. Instead, patients rely on a specialized medical formula that provides essential nutrients while limiting these specific amino acids. Additionally, patients must avoid fasting, as the body breaks down its own proteins for energy during hunger, which can trigger a dangerous metabolic crisis.
Yes, propionic acidemia can be detected prenatally if the specific genetic mutations in the PCCB gene are known in the family. Chorionic villus sampling (CVS) or amniocentesis can be performed to obtain fetal cells for genetic testing. This allows for the confirmation of whether the fetus has inherited two mutated copies of the gene. Early prenatal diagnosis enables parents to prepare for the immediate medical care required at birth and to plan for the specialized dietary and medical management that will be necessary from day one.
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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