Cytochrome and intracellular oxidase

Abstract

It was shown previously that intracellullar hæmatin compounds such as cytochrome or free hæmatin are very widely if not universally distributed in aerobic organisms and that the oxidation and reduction of cytochrome can be easily observed in intact living cells. It was also shown that in living cells oxidised cytochrome is reduced by organic molecules or metabolites activated by dehydrogenases, while the reduced cytochrome is rapidly oxidised by indophenol oxidase. Cytochrome acts in this case as a carrier between two kinds of respiratory enzymes of the cell: oxidases and dehydrogenases. This type of the respiratory mechanism of the cell is therefore composed of (1) dehydrogenases; (2) the organic molecules or metabolites; (3) the three components of cytochrome and the unbound haematin; (4) the indophenol oxidase; and (5) the molecular oxygen. The main object of this paper is a more detailed study of the functional relationship between the two components of this system: oxidase and cytochrome. For this purpose it was found important to reconstruct the oxidase-cytochrome portion of the system from its two components obtained separately from cells or tissues. Unfortunately the attempts to obtain an active oxidase preparation completely free from cytochrome have failed, and it was found impossible to extract all the three components of cytochrome from cells containing them. A great deal of information concerning the oxidase-cytochrome system can be obtained, however, by comparing the activity of the heart muscle oxidase preparation with the somewhat reduced concentration of cytochrome, with the activity of the same preparation to which is added a certain amount of component c of cytochrome extracted from yeast cells.