A pulse-radiolysis study of the manganese-containing superoxide dismutase from Bacillus stearothermophilus.
A pulse-radiolysis study of the manganese-containing superoxide dismutase from Bacillus stearothermophilus.
复制标题
嗜热脂肪芽孢杆菌含锰超氧化物歧化酶的脉冲放射分解研究。
作者：
M. E. Mcadam;Francois Lavelle;Richard A. Fox;E. Fielden
在之前的论文中，嗜热脂肪芽孢杆菌含锰超氧化物歧化酶的催化机制被证明涉及“快循环”和“慢循环”[McAdam，Fox，Lavelle & Fielden，1977（Biochem. J. 165，71-79）]。进一步的性质的酶被认为是在本文件中。在低底物浓度条件下（即当快循环占主导地位时）的脉冲辐解研究表明，酶活性随着pH值的增加而降低（6.5-10.2）。活性不受H2 O2或NaN 3的加入，但略有下降KCN。H_2O_2和还原性自由基阴离子CO_2 ~-均使天然酶的A480降低。快速催化循环的速率与温度（5-55 ° C）无关，并且随着温度增加，缓慢循环变得相对更重要。估计了速率常数的Arrhenius参数。酶的各种形式的可能的身份被认为是。
In the preceding paper the mechanism of catalysis of the manganese-containing superoxide dismutase from Bacillus stearothermophilus was shown to involve a 'fast cycle' and a 'slow cycle' [McAdam, Fox, Lavelle & Fielden, 1977 (Biochem. J. 165, 71-79)]. Further properties of the enzyme was considered in the present paper. Pulse-radiolysis studies, under conditions of low substrate concentration to (i.e. when the fast cycle predominates), showed that enzyme activity decreases as pH increases (6.5-10.2). Activity was unaffected by the addition of H2O2 or NaN3 but slightly decreased by KCN. Both H2O2 and the reducing radical anion CO2-- caused a decrease in A480 of the native enzyme. The rate of the fast catalytic cycle was independent of temperature (5-55 degrees C), and as temperature increases the slow cycle becomes relatively more important. Arrhenius parameters of the rate contants were estimated. The possible identity of the various forms of the enzyme is considered.