As an enzyme, xanthine oxidase is classified as a protein. It is mainly produced and located in the liver. It is a key enzyme in the breakdown of purine nucleotides and bases, which are components of nucleic acids like DNA and RNA. It contains the metals molybdenum and iron, so xanthine oxidase is also classified under the group of metalloproteins.
Xanthine oxidase converts hypoxanthine and xanthine into uric acid, which is then excreted by the kidneys. Most mammals, except humans, produce an enzyme called uricase. Uricase breaks down uric acid so it can be easily removed from the body.
When the liver is damaged, the hepatic cells release xanthine oxidase into the blood. High xanthine oxidase levels have been linked to diseases, including cardiovascular disease, diabetes, and hypertension. It can also exacerbate eye conditions such as cataracts and age-related macular degeneration.
Reducing xanthine oxidase and uric acid production
Natural xanthine oxidase inhibitors include plant-derived compounds such as polyphenols like flavonoids (quercetin, kaempferol, myricetin), phenolic acids (caffeic acid), and stilbenes (resveratrol). These can reduce uric acid production by blocking the xanthine oxidase enzymes, offering potential for managing gout and hyperuricaemia without the side effects caused by synthetic drugs
Xanthinuria
A deficiency of xanthine oxidase. or its cofactors. can lead to a condition called xanthinuria. When this enzyme is lacking, xanthine accumulates in the blood. Unresolved high concentrations of xanthine can eventually overload the kidneys and result in kidney failure. People who are affected are advised to forego high-purine foods and to drink lots of water to help the kidneys.
High purine food and drinks in alphabetical order
- Alcohol, especially beer and liquors
- Drinks with high-fructose corn syrup
- Organ meats (liver, kidneys, sweetbreads)
- Red meat (beef, lamb, venison)
- Seafood (shellfish, anchovies, sardines)
- Yeast extracts
When a person consumes too many purines or when the body’s xanthine oxidase is overactive, excessive levels of uric acid can be produced, leading to a condition called hyperuricemia. Too much uric acid in the body can lead to gout, kidney stones and renal failure.
Natural sources of xanthine oxidase in alphabetical order
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