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MOCS1 gene
Reviewed by Medicinsk Expert•Last updated: 2026-10-22•Gene

MOCS1 gene

The MOCS1 gene is responsible for producing proteins essential for the synthesis of molybdenum cofactor, a molecule required for the function of several vital metabolic enzymes.

Normal Function

The MOCS1 gene provides instructions for making two proteins, MOCS1A and MOCS1B. These proteins perform the first step in the biosynthesis of molybdenum cofactor. This cofactor is essential for the function of enzymes such as sulfite oxidase, aldehyde oxidase, xanthine dehydrogenase, and mitochondrial amidoxime reducing component (mARC), which help metabolize substances in the body.

Health Conditions Related to Genetic Changes

Molybdenum cofactor deficiency

Mutations in the MOCS1 gene cause molybdenum cofactor deficiency, a disorder characterized by early-onset seizures and progressive brain dysfunction (encephalopathy). It is usually fatal by early childhood.

  • Type A: At least 32 mutations in the MOCS1 gene cause this form, which accounts for approximately two-thirds of cases.
  • Mechanism: Mutations typically eliminate the function of MOCS1A or MOCS1B, impairing the biosynthesis of the cofactor.
  • Consequences: The loss of enzyme activity leads to a buildup of toxic chemicals, such as sulfite, S-sulfocysteine, xanthine, and hypoxanthine, alongside low levels of uric acid. High levels of sulfite are particularly toxic to the brain, leading to the severe neurological features of the condition.

Other Names for This Gene

  • cell migration-inducing gene 11 protein
  • MIG11
  • migration-inducing gene 11 protein
  • MOCOD
  • MOCODA
  • MOCS1A enzyme
  • molybdenum cofactor biosynthesis protein 1
  • molybdenum cofactor biosynthesis protein A
  • molybdenum cofactor synthesis-step 1 protein A-B

Genomic Location

The MOCS1 gene is found on chromosome 6.

Frequently Asked Questions

Molybdenum cofactor deficiency type A is inherited in an autosomal recessive pattern. Both parents are typically asymptomatic carriers of one pathogenic MOCS1 variant. With each pregnancy, there is a 25 percent chance that the child inherits both altered copies and develops the condition, a 50 percent chance of being an asymptomatic carrier, and a 25 percent chance of inheriting two normal gene copies.
Initial evaluation includes a rapid bedside urine dipstick for sulfites on freshly voided urine, serum uric acid testing (which shows marked hypouricemia), and quantitative plasma and urine amino acids to detect elevated S-sulfocysteine and taurine. Purine analysis will also reveal elevated xanthine and hypoxanthine. Diagnosis is definitively confirmed through targeted molecular genetic testing of the MOCS1 gene.
Both conditions present in newborns with severe encephalopathy and intractable seizures, frequently leading to misdiagnosis. However, MOCS1 deficiency is distinguished biochemically by profoundly low serum uric acid levels, elevated urine S-sulfocysteine, and positive urinary sulfite strip tests, without a history of perinatal asphyxia or birth trauma. Early differentiation is critical because standard antiepileptic drugs fail to control seizures in this metabolic disorder.
Yes. Fosdenopterin (cyclic pyranopterin monophosphate or cPMP) is an approved substrate replacement therapy specifically designed for patients with molybdenum cofactor deficiency type A. Because it bypasses the non-functioning MOCS1 enzyme to enable downstream molybdenum cofactor synthesis, starting daily intravenous infusions as early as possible after birth can arrest progressive neurological destruction and improve survival.
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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