MOCS2

MOCS2 is a gene in humans that encodes for the enzyme molybdopterin synthase. This enzyme is crucial in the biosynthesis of molybdenum cofactor (Moco), which is essential for the activity of molybdoenzymes. Molybdoenzymes play vital roles in various biological processes, including the metabolism of purines and sulfites. Mutations in the MOCS2 gene can lead to a rare disorder known as Molybdenum Cofactor Deficiency (MoCD) Type B.

Function

The MOCS2 gene, along with MOCS1 and MOCS3, is involved in the complex biosynthetic pathway that leads to the formation of molybdopterin (MPT), which is further converted into molybdenum cofactor. The MOCS2 gene product is specifically responsible for the conversion of precursor Z into molybdopterin. This step is critical, as molybdopterin serves as the ligand to which the molybdenum atom is later added, completing the molybdenum cofactor synthesis. Molybdenum cofactor is indispensable for the proper function of several important enzymes, including sulfite oxidase, xanthine dehydrogenase, and aldehyde oxidase.

Clinical Significance

Mutations in the MOCS2 gene can lead to Molybdenum Cofactor Deficiency Type B, a rare autosomal recessive metabolic disorder. This condition is characterized by a lack of functional molybdenum cofactor, which in turn leads to the accumulation of toxic levels of sulfite and neurological damage. Symptoms of MoCD Type B can include severe neurological abnormalities, developmental delay, and early childhood death. Diagnosis is typically made through biochemical analysis and genetic testing to identify mutations in the MOCS2 gene.

Genetic

The MOCS2 gene is located on chromosome 5 in humans. It consists of multiple exons that span a segment of the genome and is expressed in various tissues throughout the body. Genetic studies have identified several mutations in the MOCS2 gene that result in the loss of functional molybdopterin synthase, leading to MoCD Type B. These mutations can vary from missense mutations, which result in a single amino acid change in the enzyme, to more severe forms such as nonsense mutations or deletions that lead to a complete loss of enzyme function.

Treatment

Currently, there is no cure for Molybdenum Cofactor Deficiency Type B. Treatment is supportive and aims to manage symptoms and prevent complications. This may include measures to control seizures and manage neurological symptoms. Research into potential treatments, including gene therapy and enzyme replacement therapy, is ongoing, but these approaches are still in the experimental stages.

See Also

• Molybdenum cofactor deficiency
• Molybdenum cofactor
• Sulfite oxidase
• Xanthine dehydrogenase
• Aldehyde oxidase