Question

Illustrate relationship of xanthine and lactose

Answer 1

Xanthine is a purine base found in most tissues and fluids of the human body and in other organisms. A number of stimulants, including caffeine and theobromine, are derived from xanthine.

Lactose is a sugar found in dairy products and milk. Lactose is usually broken down by a lactase enzyme that is produced by cells in the small intestine lining.

Xanthine oxidase is one of the most important enzymes found in mammalian milk, a complex iron-sulphur molybdenum flavoprotein enzyme and a form of xanthine oxidoreductase (XOR).  Xanthine oxidase can also be obtained through a reversible or irreversible reaction from xanthine dehydrogenase (XDH). It was more than a century ago when Schardinger (1903) identified this enzyme in the form of XOR for the first time in cow’s milk.

Most of the aldehydes present in cow’s milk are considered as substrates for xanthine oxidase, contributing to oxidative reactions in milk. The association between the activity of xanthine oxidase and oxidative deterioration of milk and dairy foods has shown that a high level of xanthine oxidase was associated with the occurrence of a spontaneously-oxidized flavor in milk and the inhibitors of this enzyme could prevent the off-flavor development.

Health concerns regarding xanthine oxidase-containing milk foods

The oxidation of hypoxanthine and xanthine to urate, the formation of superoxide radicals by Xanthine oxidase, can promote the level of oxidation in the body leading to consideration of xanthine oxidase as an important biological source of superoxide radicals. These superoxide radicals can react with DNA, cells, and proteins and cause damage/toxicity to cells. In addition, reactive oxygen species can be coupled with reactive nitrogen signalling and contribute to a central part of myocardial and vascular function, indicating the link of excess amount of xanthine oxidase with cardiovascular health. Regarding gout, which may be caused by xanthine oxidase, as this enzyme is a metabolic pathway in the formation of urate, allopurinol (as the inhibitor of xanthine oxidase) is used for the treatment of the disease.

For more information: https://www.researchgate.net/publication/326014766_Xanthine_Oxidase_in_Dairy_Foods#pf6