Prosthetic groups of the cytochromes present in Corynebacterium diphtheriae with especial reference to cytochrome a

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Abstract
The cells of C. diphtheriae, when grown at iron levels sufficient to inhibit the excretion of toxin and coproporphyrin, showed a 5- to 10-fold increase of heme components over the level present when toxin and porphyrin excretion are maximal. The presence of cytochrome oxidase (cytochrome a complex) and cytochrome b were confirmed spectroscopically. Methods for the separation of the 2 main heme prosthetic groups are described. Crystalline protohemin, which is assumed to be derived at least in part from cytochrome b, and a dichroic heme, presumably from the cytochrome a complex, were obtained. The dichroic heme was identified with the heme of cytochrome a of ox-heart muscle and further studies on its characteristics were made on material from this more accessible source. The free porphyrin, like the heme from cytochrome a, reacted with cysteine and hydroxylamine. Tests indicated that this heme contained at least one aldehyde group.