Biochemical Study on Terminal Oxidase of Bacterial Respiratory Chain

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Cytochrome o oxidase, which functions extensively in a wide variety of bacteria, was investigated by comparing its structure and function among several bacteria such as Escherichia, Gluconobacter, Acetobacter and Pseudomonas. The oxidase was also oxidase was also compared in their function with another terminal oxidase coexistion in the respective strains.1) Terminal oxidase of E. coli: The respiratory chain contains cytochromes o and d as terminal oxidases, the synthesis of which is regulated by oxygen concentration in the medium. The cytochrome o oxidase was able to react with ubiquinol, and to generate a membrane potential in the reconstituted proteoliposomes. Furthermore, the oxidase was able to reconstitute glucose oxidase respiratory chain with Q-8 and glucose dehydrogenase (GDH) in the proteoliposomes.2) Terminal oxidase of G. subboxydans: The respiratory chain branched with cytochrome o and a non-energy-generating bypass consisting of a cytochrome c. The bypass only was changed … More by pH of the medium. The cytochrome o had almost the same structure and function as that of E. coli, and thus was able to react with ubiquinol and to generate an energy. However, the oxidase was somewhat different immunologically from e. coli cytochrome o. Furthermore, the oxidase was also able to reconstitute glucose oxidase respiratory chain with Q-10 and GDH.3) Terminal oxidase of A. aceti: The respiratory chain contained cytochromes o and a as terminal oxidases, which changed depending on culture conditions, shaking or stationary. The cytochrome o had almost the same structure and function as the enzyme described above. Furthermore, the structure and function of the cytochrome a was similar to those of the cytochrome o. At this moment, however, the relationship between the cytochromes o and a is not clear.4) Terminal oxidase of P. aerugiosa: The respiratory chain had cytochrome o as the terminal oxidase, and further a cyanide insensitive bypass. The cytochrome o was extensively different from others, reacting chtochrome c but not with ubiquinol, but not different in the property to generate an energy. Less