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CA5A gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

CA5A gene

The CA5A gene provides instructions for making an enzyme essential for maintaining the body's acid-base balance and supporting energy production in cells.

Normal Function

The CA5A gene provides instructions for making an enzyme called carbonic anhydrase VA. This enzyme helps convert carbon dioxide to a substance called bicarbonate, which is necessary to maintain the proper acid-base balance in the body for most biological reactions to proceed properly.

The carbonic anhydrase VA enzyme is particularly important in the liver, where it provides bicarbonate needed by four enzymes in the energy-producing centers of cells (mitochondria):

  • Carbomoyl phosphate synthetase-1: Involved in the urea cycle, which processes excess nitrogen and prevents it from accumulating as ammonia, a substance that is toxic to the brain.
  • Pyruvate carboxylase: Involved in the production of the simple sugar glucose (gluconeogenesis) in the liver.
  • Propionyl-CoA carboxylase: Helps break down certain protein building blocks (amino acids).
  • 3-methylcrotonyl-CoA carboxylase: Helps break down certain protein building blocks (amino acids).

Health Conditions Related to Genetic Changes

Carbonic anhydrase VA deficiency

At least three CA5A gene mutations have been identified in people with carbonic anhydrase VA deficiency. This inherited disorder is characterized by potentially life-threatening episodes of:

  • Poor feeding
  • Vomiting
  • Weight loss
  • Tiredness (lethargy)
  • Rapid breathing (tachypnea)
  • Seizures
  • Coma

The risk of these episodes is thought to decline after childhood. Mutations in the CA5A gene result in absent or impaired carbonic anhydrase VA enzyme function, leading to reduced bicarbonate production. Insufficient bicarbonate results in impaired control of acid-base balance and reduces the activity of the four affected mitochondrial enzymes. Studies suggest that a related enzyme produced from the CA5B gene may increasingly compensate for the lack of carbonic anhydrase VA as affected individuals mature, which may result in a reduced risk of disease episodes after childhood.

Other Names for This Gene

  • CA-VA
  • CA5
  • CA5AD
  • carbonate dehydratase VA
  • carbonic anhydrase 5A, mitochondrial precursor
  • carbonic anhydrase V, mitochondrial
  • carbonic anhydrase VA, mitochondrial
  • carbonic dehydratase
  • CAV
  • CAVA
  • GS1-21A4.1

Frequently Asked Questions

Infants with CA5A deficiency often show poor feeding, vomiting, and weight loss within the first few weeks of life. They may also develop rapid breathing (tachypnea), lethargy, and in severe cases seizures or brief periods of unconsciousness. Parents should seek immediate medical attention if these symptoms appear, especially if they worsen after illness or fasting.
Diagnosis starts with a clinical evaluation and laboratory tests that reveal metabolic acidosis and low bicarbonate levels. A definitive diagnosis is made by sequencing the CA5A gene to identify pathogenic mutations. In some cases, enzyme activity assays on liver tissue or cultured cells can confirm reduced carbonic anhydrase VA function.
While the risk of acute episodes decreases after childhood, adults with CA5A mutations may experience subtle symptoms such as fatigue, mild headaches, or occasional metabolic disturbances during stress. Adults should monitor for unexplained fatigue, especially after illness or prolonged fasting, and keep regular follow‑ups with a metabolic or genetic specialist to adjust treatment if needed.
Management focuses on maintaining a stable acid‑base balance. This includes frequent, small feedings of a high‑calorie, high‑protein diet, bicarbonate supplementation to correct acidosis, and close monitoring of blood gases. During illness or fasting, parents should increase fluid intake and consider intravenous bicarbonate if acidosis worsens. Early intervention with a metabolic specialist can reduce the frequency of severe episodes.
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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