Synthesis of 2-Demethyl Vitamin K2 and the Cytochrome System in Haemophilus

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White, David C. (University of Kentucky College of Medicine, Lexington). Synthesis of 2-demethyl vitamin K2 and the cytochrome system in Haemophilus. J. Bacteriol. 89:299–305. 1965.—The synthesis of the respiratory quinone, 2-demethyl vitamin K2, is stimulated in Haemophilus parainfluenzae under conditions which provoke the synthesis of the cytochrome system. However, the various components of the electron-transport system can be formed in different proportions. The primary flavoprotein dehydrogenases are readily dissociated from the membrane without affecting the content of membrane-bound quinone, cytochrome b1, or the cytochrome oxidases. These dehydrogenases must be membrane-bound to function, and each can be formed at a different rate. Molar ratios of various constituents of the electron-transport chain were calculated by use of reasonable extinction coefficients for the cytochromes. The molar ratio of quinone to cytochrome c1 goes from 40 to 3 as the quinone content increases eightfold during the growth cycle. Similarly, the molar ratio of quinone to cytochrome oxidase a2 varies from 27 to 17, and then increases to 31 as cytochrome oxidase a1 assumes the oxidase function. The molar ratio of quinone to cytochrome b1 remains 14 to 1 over a sixfold increase in both components measured in a mutant where cytochrome c1 does not obscure cytochrome b1. A similar consistency was noted between the quinone and cytochrome b1 formation in the hemin-requiring H. influenzae.

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