THE ENZYME-SUBSTRATE COMPOUNDS OF BACTERIAL CATALASE AND PEROXIDES
THE ENZYME-SUBSTRATE COMPOUNDS OF BACTERIAL CATALASE AND PEROXIDES
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DOI：
10.1042/bj0460402
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发表时间：
1950-01-01
影响因子：
4.1
通讯作者：
HERBERT, D
中科院分区：
文献类型：
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作者：
CHANCE, B;HERBERT, D
细菌过氧化氢酶与H2O2、甲基-H2O2和乙基-H2O2形成初级和次级酶-底物复合物。细菌和红细胞过氧化氢酶-甲基-H2O2复合物的光谱在Soret带区域几乎相同。然而，细菌和红细胞过氧化氢酶的初级H2O2复合物的Soret带之间存在定量差异。在细菌过氧化氢酶存在下，H2O2分解的速度常数（20 - 25 [度]）为5.3 × 107 M-1秒。1，并且可以与红细胞过氧化氢酶的3.5 × 107的值进行比较;即，速度常数（或Kat. F.值）为1.5：1。细菌过氧化氢酶与H2O2结合的速度常数约为6 x 107 [图片]-1秒。1.细菌过氧化氢酶与甲基或乙基H2O2结合的速度常数分别为2.2 x 105和2.8 x 103 [image]-1sec-1。这些值比红细胞过氧化氢酶的相应值慢约10倍。主要的细菌过氧化氢酶-过氧化物复合物与受体反应的机制，发现获得相应的红细胞过氧化氢酶-过氧化物复合物，只有绿色主要复合物似乎参与这些反应。专属性似乎遵循相同的模式;评价了亚硝酸盐、甲醛、甲酸盐、甲醇、乙醇和丙醇的速度常数。在细菌过氧化氢酶与底物或受体的反应中，反应速度常数的值取决于底物或受体分子的大小，其程度比红细胞过氧化氢酶的情况大得多;大分子的反应比小分子慢得多。这种更大的依赖性被解释为表明细菌过氧化氢酶的血红素被"掩埋"在蛋白质分子中的程度比红细胞过氧化氢酶的血红素更大。然而，细菌过氧化氢酶的血红素与H2O2的反应比红细胞calase的血红素更迅速。有人建议，接近的蛋白质组的细菌过氧化氢酶的血红素增强其活性对分子的血红素是可访问的。
Bacterial catalase formed primary and secondary enzyme-substrate complexes with H2O2, methyl-H2O2 and ethyl-H2O2. The spectra of the bacterial and erythrocyte catalase-methyl-H2O2 complexes in the region of the Soret band were nearly identical. However, a quantitative difference existed between the Soret bands of the primary H2O2 complex of bacterial and erythrocyte catalases. The velocity constant (at 20-25[degree]) for the decomposition of H2O2 in the presence of bacterial catalase was 5.3 x 107M-1sec.-1 for a four-hematin catalase, and might be compared with the value of 3.5 x 107 for erythrocyte catalases; i.e., the ratio of the velocity constants (or of the Kat. f. values) for the 2 enzymes is 1.5:1. The velocity constant for the combination of bacterial catalase with H2O2 was about 6 x 107 [image]-1sec.-1. The velocity constants for the combination of bacterial catalase with methyl- or ethyl-H2O2 were 2.2 x 105 and 2.8 x 103 [image] -1sec-1, respectively. These values were about 10 times slower than the corresponding values for erythrocyte catalases. The primary bacterial catalase-peroxide complexes reacted with acceptors according to the mechanisms found to obtain for the corresponding erythrocyte catalase-peroxide complexes; only the green primary complexes appeared to be involved in these reactions. The specificity appeared to follow an identical pattern; velocity constants were evaluated for nitrite, formaldehyde, formate, methanol, ethanol and propanol. In the reactions of bacterial catalase with substrates or acceptors, the values of the reaction velocity constants were dependent on the size of the substrate or acceptor molecule to a much greater extent than was found to be the case with erythrocyte catalase; large molecules reacted much more slowly than small ones. This greater dependence was interpreted to indicate that the hematins of bacterial catalase were "buried" in the protein molecule to a greater extent than were the hematins of erythrocyte catalase. Nevertheless, the hematins of bacterial catalase reacted with H2O2 more rapidly than did the hematins of erythrocyte calatase. It was suggested that the proximity of the protein groups to the hematins of bacterial catalase enhanced their activity towards molecules to which the hematins were accessible.