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CPS1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

CPS1 gene

The CPS1 gene provides instructions for an enzyme that plays a critical role in the urea cycle, helping the body process and excrete toxic nitrogen.

Normal Function

The CPS1 gene provides instructions for making the enzyme carbamoyl phosphate synthetase I. This enzyme participates in the urea cycle, a series of reactions that occurs in liver cells. The urea cycle processes excess nitrogen, generated when protein is used by the body, into a compound called urea that is excreted by the kidneys. Excreting the excess nitrogen prevents it from accumulating in the form of ammonia, which is toxic.

The specific role of carbamoyl phosphate synthetase I is to control the first step of the urea cycle, a reaction in which excess nitrogen compounds are incorporated into the cycle to be processed.

Health Conditions Related to Genetic Changes

Carbamoyl phosphate synthetase I deficiency

Approximately 10 mutations that cause carbamoyl phosphate synthetase I deficiency have been identified in the CPS1 gene. A mutated CPS1 gene may result in an enzyme that is shorter than normal, the wrong shape, or may prevent the enzyme from being produced at all.

The shape of an enzyme affects its ability to control a chemical reaction. If the carbamoyl phosphate synthetase enzyme is misshapen or missing, it cannot fulfill its role in the urea cycle. Excess nitrogen is not converted to urea for excretion, and ammonia accumulates in the body. Ammonia is toxic, especially to the nervous system, so this accumulation causes neurological problems and other signs and symptoms of the deficiency.

Other disorders

One common alteration (polymorphism) in the CPS1 gene has been associated with an increased risk of circulatory problems in newborns and in individuals who have received bone marrow transplants. This genetic change results in the amino acid asparagine being substituted for the amino acid threonine at position 1405 in the protein sequence (written as Thr1405Asn or T1405N).

Researchers believe that this polymorphism may reduce the production of a compound called nitric oxide (NO). Normally, nitric oxide causes blood vessels to expand (dilate), which reduces blood pressure. A reduced amount of nitric oxide could lead to circulatory problems.

Other Names for This Gene

  • carbamoyl phosphate synthase I
  • carbamoyl-phosphate synthase 1, mitochondrial
  • carbamoyl-phosphate synthase, mitochondrial precursor
  • carbamoylphosphate synthetase I
  • CPSase I
  • CPSM_HUMAN

Genomic Location

The CPS1 gene is found on chromosome 2.

Frequently Asked Questions

Because CPS1 deficiency is autosomal recessive, each sibling has a 25 % chance of being affected if both parents carry a mutation. Prenatal testing or pre‑implantation genetic diagnosis can identify affected embryos. Carrier testing for extended family members is also recommended.
low‑protein diet (typically 0.8–1.0 g/kg/day) reduces ammonia production. Protein is usually divided into small, frequent meals. Some patients benefit from supplementing with essential amino acids that are not metabolized by the urea cycle. Lactulose or rifaximin may be added to reduce intestinal ammonia absorption.
ny sudden increase in lethargy, vomiting, confusion, or seizures—especially after a high‑protein meal, illness, or fasting—may indicate hyperammonemia. Immediate medical attention is critical; treatment often involves intravenous glucose, nitrogen‑scavenging drugs, and sometimes dialysis.
The diagnosis is confirmed by measuring plasma ammonia levels (often markedly elevated), plasma citrulline (low or normal), and urinary orotic acid (high). Genetic testing of the CPS1 gene identifies pathogenic variants. Enzyme activity assays in liver tissue or cultured fibroblasts can also be performed.
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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