吸光度
化学
反应速率常数
荧光
反应中间体
尿酸氧化酶
催化作用
分光光度法
反应机理
过氧化物
光化学
反应速率
动力学
酶
色谱法
有机化学
物理
量子力学
作者
Kalju Kahn,Peter A. Tipton
出处
期刊:Biochemistry
[American Chemical Society]
日期:1998-07-29
卷期号:37 (33): 11651-11659
被引量:112
摘要
The oxidation of urate catalyzed by soybean urate oxidase was studied under single-turnover conditions using stopped-flow absorbance and fluorescence spectrophotometry. Two discrete enzyme-bound intermediates were observed; the first intermediate to form had an absorbance maximum at 295 nm and was assigned to a urate dianion species; the second intermediate had an absorbance maximum at 298 nm and is believed to be urate hydroperoxide. These data are consistent with a catalytic mechanism that involves formation of urate hydroperoxide from O2 and the urate dianion, collapse of the peroxide to form dehydrourate, and hydration of dehydrourate to form the observed product, 5-hydroxyisourate. The rate of formation of the first intermediate was too fast to measure accurately at 20 °C; the second intermediate formed with a rate constant of 32 s-1 and decayed with a rate constant of 6.6 s-1. The product of the reaction, 5-hydroxyisourate, is fluorescent, and its release from the active site occurred with a rate constant of 31 s-1.
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