Pliugacheva E I, Metelitsa D I
Biokhimiia. 1986 Aug;51(8):1262-7.
The gluconic fragment of strophantin K oxidation by sodium metaperiodate yields a dialdehyde derivate conjugated with catalase. The conjugate obtained contains 11 molecules of cardiac glucoside. Adsorption and circular dichroism spectra of the native enzyme and its conjugate were compared and structural differences between both samples were revealed. The kinetics of ethanol oxidation into acetaldehyde by cumene hydroperoxide was studied at 30 degrees C in the phosphate buffer pH 6.6; this reaction was shown to proceed with the participation of catalase and its cat-str conjugate. The catalytic constants for catalase are 1.2-1.5 times as high as those for cat-str, whereas the Km values for both substrates for the conjugate as 1.5-2 times as high as those for catalase. Catalase modification by strophantin K increases the enzyme thermostability up to the isokinetic point of 40 degrees C; above this threshold the cat-str thermostability decreases as compared with the native enzyme. The thermodynamical activation parameters for catalase and cat-str inactivation were determined.
高毒毛旋花子苷K经偏高碘酸钠氧化得到的葡萄糖酸片段可产生一种与过氧化氢酶共轭的二醛衍生物。所得共轭物含有11个强心苷分子。比较了天然酶及其共轭物的吸附光谱和圆二色光谱，揭示了两个样品之间的结构差异。在30℃、pH 6.6的磷酸盐缓冲液中研究了过氧化氢异丙苯将乙醇氧化为乙醛的动力学；结果表明，该反应在过氧化氢酶及其cat-str共轭物的参与下进行。过氧化氢酶的催化常数是cat-str的1.2 - 1.5倍，而共轭物对两种底物的米氏常数是过氧化氢酶的1.5 - 2倍。高毒毛旋花子苷K对过氧化氢酶的修饰将酶的热稳定性提高到40℃的等动力学点；高于此阈值，cat-str的热稳定性与天然酶相比降低。测定了过氧化氢酶和cat-str失活的热力学活化参数。
