Introduction
Xanthine oxidase is an enzyme that can not only catalyze the generation of hypoxanthine into xanthine, and then generate uric acid, but also directly catalyze the formation of uric acid from xanthine, which is an enzyme containing molybdenum, non-heme iron, inorganic sulfide and FAD, which exists in milk, animals (especially the liver and kidney of birds), insects and bacteria. Xanthine oxidase has a molecular weight of 10 tens of thousands to 30 tens of thousands, and the substrate has a wide range of oblivionism, in addition to purine derivatives as electron donors, it can also be used as electron donors for pteridine derivatives and aldehydes (to generate carboxylic acids) as electron donors, and hydroxyl compounds are generated on the surface, and oxygen atoms are ** in water. There are many xanthine oxidase electron acceptors, including molecular oxygen, nitrate, benzoquinone, nitro compounds, NAD, ferredoxin, etc., but they vary according to the ** of the enzyme. Peroxides are formed during the reaction, causing a chain reaction. Store at a temperature of 2-8 degrees.
Chemical reactions
Xanthine oxidase catalyzes the following reaction: hypoxanthine + H2O + O2 xanthine + H2O2Xanthine + H2O + O2 uric acid + H2O2Xanthine + H2O + 2O2 uric acid + 2O2- (superoxide anion) + 2H+ (hydrogen ion).
Features:
1. Xanthine oxidase appears as a light yellow liquid in appearance, and it is a crystalline suspended in 23mol L ammonium sulfate, L0mmol L sodium phosphate buffer solution, containing 1mmol L EDTA, 1mmol L sodium salicylate, pH value is about 78. It is a flavin protein containing iron-molybdenum. 2. It can oxidize hypoxanthine, xanthine and aldehyde, etc., and the optimal pH value is 82. The isoelectric point is 53-5.4。
3. The activator is oxygen, and the inhibitors include heavy metal ions, cyanide, aldehydes, allopurinol, phosphate, imidazole, sodium chloride and potassium chloride. 4. The crude enzyme can be stored for several weeks at 2 o'clock without reducing its viability, and can be stored for a long time under freezing conditions.