3-羟基黄嘌呤的酶促氧化生成3-羟基尿酸。

Enzymic oxidation of 3-hydroxyxanthine to 3-hydroxyuric acid.

Bergmann F, Levene L

Biochim Biophys Acta. 1977 Apr 12;481(2):359-63. doi: 10.1016/0005-2744(77)90269-8.

Abstract

Bovine milk xanthine oxidase (xanthine:oxygen oxidoreductase, EC 1.2.3.2) oxidises 3-hydroxyxanthine slowly to 3-hydroxyuric acid; the 1-methyl derivative of 3-hydroxyxanthine is attacked about twice as fast. 2. The pH optimum for the reaction of 2-hydroxyxanthine is near 5, i.e. the neutral form of this substrate is attacked much faster than the anion. Probably in the "active" form of the latter, the negative charge is located mainly in the imidazole ring, thus inhibiting nucleophilic attack at C-8.

摘要

牛乳黄嘌呤氧化酶（黄嘌呤：氧氧化还原酶，EC 1.2.3.2）将3-羟基黄嘌呤缓慢氧化为3-羟基尿酸；3-羟基黄嘌呤的1-甲基衍生物的反应速度约快两倍。2. 2-羟基黄嘌呤反应的最适pH接近5，即该底物的中性形式比阴离子形式的反应速度快得多。可能在后者的“活性”形式中，负电荷主要位于咪唑环上，从而抑制了对C-8的亲核攻击。