Xanthine Oxidase  别名：EC 1.1.3.22; 黄嘌呤氧化酶

黄嘌呤氧化酶(XOD)是一种黄嘌呤氧化还原酶，能够催化次黄嘌呤生成尿酸和过氧化氢，是体内核酸代谢中的重要酶之一。当与嘌呤核苷磷酸化酶和尿酸酶偶联时，黄嘌呤氧化酶(XOD)可用于无机磷、5’-核苷酸酶和腺苷脱氨酶的检测。黄嘌呤氧化酶(XOD)还具有蛋白水解活性。

牛乳中提取的黄嘌呤氧化酶用于：

制备黄嘌呤氧化酶（XO）溶液 ，用于5-（二乙氧基磷酰）-5-甲基-1-吡咯啉N-氧化物(DEPMPO)自旋捕获分析
体外 XO检测，筛选越南药用植物XO抑制活性
确定XO活性的标准品
检测二十二碳六烯酸（DHA）协同效应的标准品

单位定义

一单位每分钟能够将1.0 μmole木糖转化成尿酸，PH7.5, 37℃。

Isoelectric point: 4.0。
Michaelis constant: 1.4×10 M (Xanthine)。
Optimum pH: 7.0~ 7.5。
pH Stability: 6.0~9.5(30℃,16hr)。
Thermal stability: < 55℃ (pH 7.5, 20min)。
Inhibitors: Ag, Hg。

应用参考（摘自公开文献）

XO activity determination

Serum XO activity was measured by the method of Prajda and Weber (1975), where activity is measured by determination of uric acid from xanthine. Serum samples were incubated for 30 min at 37-C in 3 ml of the phosphate buffer (pH 7.5, 50 nM) containing xanthine (4 mM). The reaction was stopped by addition of 0.1 ml 100% (w/v) TCA and the mixture was then centrifuged at 4000 g for 20 min. Urate was determined in the supernatant by measuring absorbance at 292 nm against blank and expressed as U/l serum. A calibration curve was constructed by using 10–50 mU/ml concentrations of standard XO solutions. One unit of activity was defined as 1 Amol of uric acid formed per minute at 37°C, pH 7.5.

https://pubmed.ncbi.nlm.nih.gov/15972243/