81 by: Zachary Darwin

Student – Zachary Darwin

Enzyme & EC # – Xanthine oxidase: EC originally 1.1.3.22, now correctly classified as EC 1.17.3.2

Xanthine oxidase is primarily found in the liver and small intestines of humans. It can also be present in other tissues, including the kidneys and lungs. Xanthine oxidase plays a big role in purine metabolism. It catalyzes the oxidation of hypoxanthine to xanthine and then xanthine to uric acid. This process helps in the breakdown of purine nucleotides, which are components of DNA and RNA. By converting these substances into uric acid, xanthine oxidase aids in eliminating excess purines from the body. However, an overproduction of uric acid can lead to conditions like gout. This is where the inhibitor allopurinol helps in this case by reducing uric acid levels. Xanthine oxidase generates reactive oxygen species, including hydrogen peroxide and superoxide radicals, as byproducts of its activity. These reactive species can contribute to oxidative stress and are linked to various diseases, including gout and cardiovascular conditions.

References

Aziz, N., & Jamil, R. T. (2020). Biochemistry, Xanthine Oxidase. PubMed; StatPearls Publishing. https://www.ncbi.nlm.nih.gov/books/NBK545245/

ExplorEnz: Search Results. (2024). Enzyme-Database.org. https://www.enzyme-database.org/query.php?name=xanthine+oxidase

Substrate orientation and the origin of catalytic power in xanthine oxidoreductase – Scientific Figure on ResearchGate. https://www.researchgate.net/figure/The-reaction-mechanism-of-xanthine-oxidase-The-reaction-is-initiated-by-proton_fig1_286406227