Xanthine Oxidase from bovine milk

Research area: Cell Cycle

Xanthine Oxidase (XO) belongs to the class of complex metalloflavoproteins. It is produced by oxidation of sulfhydryl residues or by proteolysis of xanthine dehydrogenase (XDH). XO is characterized with two flavin molecules (FAD), two molybdenum atoms, and eight iron atoms bound per enzymatic unit.

Formerly E.C. 1.1.3.22

Xanthine Oxidase from bovine milk has been used:

• as a source for superoxide generation
• for the degradation of hypoxanthine
• for the detection of reactive oxygen species (ROS) in lipid model by electron spin resonance (ESR) spin trap method
• as a constituent of assay mixture in xanthine oxidase inhibition assay

Xanthine Oxidase (XO)catalyzes the hydroxylation of hypoxanthine to xanthine and xanthine to uric acid. Xanthine oxidase activity is inhibited by folic acid. [7] and various other inhibitors including 3,4-Dihydroxy-5-nitrobenzaldehyde (DHNB), febuxostat and allopurinol. XO and xanthine dehydrogenase (XDH) plays a vital role in the last two steps in the formation of urate. Elevated levels of XO has been observed in the serum of chronic liver disease patients. Therefore, XO can be used as a biomarker for the detection of liver disease.

Xanthine oxidase activity is inhibited by folic acid.

Xanthine oxidase is a molybdenum-containing enzyme that is found in the cytosol, and may be strongly inhibited by flavonoids. It plays a vital role in the metabolism of some drugs, as well as purines and pyrimidines. It is also known to be a biological source of reactive oxygen species.

One unit will convert 1.0 μmole of xanthine to uric acid per min at pH 7.5 at 25 °C. Approx. 50% of the activity is obtained with hypoxanthine as substrate.

Suspension in 2.3 M (NH₄)₂SO₄, 10 mM sodium phosphate buffer, pH 7.8, containing 1 mM EDTA and 1 mM sodium salicylate

Chromatographically purified

Protein determined by biuret