Agronomy and Horticulture, Department of


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Published in JOURNAL OF BIOLOGICAL CHEMISTRY 205:1 (1953), pp. 423-433.


It was shown recently that the poky strain of Neurospora accumulates large amounts of cytochrome c, but is deficient in cytochromes a and b and thus in cytochrome oxidase and succinic acid oxidase activities (1). These findings, which suggest that respiration in poky does not utilize the cytochrome system, led to a study of the respiratory system of poky compared with that of wild type. The experiments reported here are concerned with the effects of the inhibitors cyanide and azide on the respiration of intact mycelium of poky and wild type, the oxygen uptake of cell-free extracts in the oxidation of their endogenous substrates, the cofactor requirement for this oxidation, and the effects of azide and of oxygen tension. Evidence presented confirms that, in poky, respiration does not depend upon the cytochromes, but upon another terminal oxidase system in which flavin- adenine dinucleotide (FAD) enzymes appear to be concerned.