Autoxidation of Ascorbic Acid Catalyzed by the Copper(II) Bound to L-Histidine Oligopeptides, (His)iGly and Acetyl-(His)iGly (i=9, 19, 29). Relationship between Catalytic Activity and Coordination Mode.
作者:Jun-ichi UEDA、Akira HANAKI、Keiichiro HATANO、Terumi NAKAJIMA
DOI:10.1248/cpb.48.908
日期:——
Spectroscopic and kinetic studies on the autoxidation of ascorbic acid catalyzed by copper complexes of histidine oligopeptides, (His)iGly (i=4, 9, 19, 29), and their acetyl derivatives, Ac-(His)iGly (i=9, 19) have been carried out at pH 4.4 and 25 degrees C under dioxygen. The reaction was monitored at 260 nm using a stopped-flow spectrophotometric technique. The reaction fitted the "Michaelis- Menten"
组氨酸寡肽(His)iGly(i = 4、9、19、29)及其乙酰基衍生物Ac-(His)iGly(i = 9, 19)已经在pH 4.4和25℃在双氧下进行。使用停止流分光光度法在260 nm处监测反应。该反应符合“ Michaelis-Menten”机理,抗坏血酸盐被“ Ping-Pong”机理氧化。与寡肽(i>或= 9)络合的Cu(II)相对于含水Cu(II)使反应增强约两倍。催化活性取决于与组氨酸残基的数目有关的分子量和铜结合位点的配位方式。圆二色性(CD)实验的结果表明存在两种类型的Cu(II)。包含在至少六个组氨酸残基组成的咪唑簇中的具有催化活性的Cu(II),在520和630 nm处显示dd跃迁带,并且易于分解,可增强自氧化作用。Ac-(His)19Gly可能容纳约三个活性Cu(II)离子。与末端H2N-XY-His-部分紧密配合的Cu(II),其中X和Y表示氨基酸,抑制自氧化作用,并在480和550