Abstract: This work aimed to study the characteristics of xanthine oxidase (XOD) by using RP-HPLC to determine formation amount of uric acid, the product by the enzyme. The results showed the optimal reaction pH and temperature of XOD in 50 mmol/L Tris-HCl buffer are 8.4 and 37 ℃, respectively. But the enzyme is still stable at the pH ranging from 7.0 to 9.0 and below 40 ℃. The Km value of this enzyme is calculated as being 0.043 mmol/L. Further experimental results revealed that XOD can be activated by sodium salicylate, cysteine, histamine, (NH4)2SO4 and EDTA, but be inhibited by some metal ions (especially Ag+ and Hg2+), urea, 6-aldehyde purine and 2-amino-4-hydroxypteridine 6-aldehyde. The activity of XOD is hardly affected by low concentration of surface-activator such as Tween 80, SDS and Triton X-100.

Key words: xanthine oxidase, enzymologic characteristics, stability