Cytochromes and some respiratory enzymes in mitochondria from the spadix of Arum maculatum

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Abstract
The cytochromes of mitochondria from young and mature spadices of A. maculatum were compared. Cytochrome b7 occurs in young mitochondria, but in a smaller concentration relative to that of cytochrome c than in the mature, A method is described for measuring the concentration of cytochromes a + a3 in tissue preparations, by comparison with a chlorinated resorufin derivative. The concentrations of a, b and c cytochromes in Arum mitochondria were estimated. The uptake of oxygen by Arum-spadix mitochondria in the presence of succinate or malate increased as the spadix matured. Cyanide and antimycin A only partially inhibited the respiration of succinate and malate. Antimycin A gave smaller inhibitions than cyanide. It is suggested that there is an increase in the importance of the pathway insensitive to cyanide and antimycin relative to the cytochrome c oxidase pathway as the spadix matures. The succinic-cytochrome c reductose of mature mitochondria was completely inhibited by antimycin A. Antimycin A inhibited the oxidation of cytochromes b and two components with bands at 553 and 563 mu. The oxidation of cytochrome b7 was not inhibited. The respiration of the whole young spadix was stimulated by m[image]-cyanide, even though the oxidation of succinate by the mitochondria could be inhibited as much as 80%.