Terminal oxidases of micrococcus denitrificans
1957; Elsevier BV; Volume: 25; Linguagem: Inglês
10.1016/0006-3002(57)90475-4
ISSN1878-2434
Autores Tópico(s)Cassava research and cyanide
Resumo1. A cytochrome c oxidase was partially purified from the facultative anaerobe, Micrococcus denitrificans. This enzyme was shown to be associated with the particulate matter of the cell and was capable of oxidizing reduced mammalian cytochrome c. A procedure for purification of this oxidase is given. 2. The optimum pH for the bacterial cytochrome oxidase was found to be from 7.0 to 7.4. Activity was not increased by the addition of aluminum ion to the assay system, and magnesium and manganous ions had no effect upon the activity. The oxidase activity was 98% inhibited by 5·10−4M cyanide, while a similar concentration of azide inhibited only 55%. Carbon monoxide affected 100% inhibition which was light-reversible. 3. The reduced spectrum of a purified cytochrome oxidase fraction had maxima at 421, 522 and 553 mμ, while the corresponding maxima for a cell-free extract were at 417, 522 and 551 mμ, indicating removal of cytochrome c during the purification procedure and concentration of cytochrome c1 in the particulate matter containing the cytochrome oxidase. Cell-free extracts had ability to perform oxidative phosphorylation, with an average P:O ration of 0.39 when oxidizing reduced cytochrome c. 4. A cyanide-insensitive DPNH oxidase, which appeared to be a soluble flavoprotein, was partially purified from cells of M. denitrificans. The Michaelis constant with respect to DPNH was determined to be 1.5·10−6 moles per liter. The activation energy was found to be 14,900 cal per mole. A comparison of these two oxidase as a terminal oxidative enzyme was determined, showing that the DPNH oxidase can accommodate approximately one-half as much oxygen uptake as the cytochrome oxidase system.
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