The porphyrin of component c of cytochrome and its relationship to other porphyrins

Abstract

Of the hæmatin compounds present in the cell, component c of cytochrome alone can be readily obtained in solution by extraction with water of either dry or acetone yeast (Keilin, 1925). Recently a method for extracting and concentrating this pigment from yeast has been described, and it was found that the component c thus obtained has the same properties as it has in intact living cells or in the extracts of dry of acetone yeast cells (Keilin, 1930, pp. 421-423). It was shown previously that cytochrome c is a hæmochromogen which differs from the usual hæmochromogen compounds in two important properties, namely, in not being autoxidisable and in not forming a carbon monoxide compound. It was also shown that, without changing it absorption spectrum, the component c can be easily modified in such a way as to show the properties of an ordinary hæmochromogen (Keilin, 1925, 1926). As the various hæmochromogens obtained from cytochrome c have the positions of the absorption bands very different from those of protohæmochromogens it was clear that the iron-porphyrin portion of its molecule is completely different from the ordinary protohæmatin. A series of facts discussed in previous papers suggested, however, that cytochrome originated from the ordinary protohæmatin which is also present in all cells of aerobic organisms. The object of the experiments described in this paper is the study of the porphyrin portion of cytochrome c and its relationship to other prophyrins, especially to protoporphyrin.