Comparative Biochemistry of Cytochrome C.

To elucidate the origin of life on the earth and its evolution, one of the best methods is to classify organisms on the basis of their biochemical properties, and for this comparative biochemical studies are necessary. Such studies have been made in a variety of studies by various workers. For example, hemoglobins were studied by Pauling and Zuckerkandl (1) a.nd Haurowitz and Hardin (2)) the visual pigments by Wald (3)) and lactate dehydrogenases by Kaplan et al. (4). These comparative studies were made only on animals. Studies on the visual pigments are inevitably limited to animals with eyes, whereas studies on hemoglobins were principally on animals with blood containing hemoglobin. Furthermore, it is known that these materials vary appreciably under the different environmental conditions in which the organisms live (3). This may mean that although the phylogenies established on the basis of comparative biochemical studies on such materials are very similar to those established from anatomical characters, it is difficult from such studies to distinguish the more primitive properties of these materials which the ancestral organisms may have had. Cytochromes are present in all aerobic organisms and in some anaerobic microorganisms, and are very fundamental components. Thus, it seems very advantageous to select cytochromes as materials for comparative biochemical studies. Among the cytochromes, cytochrome c is generally easily extractable by salt solution, and the procedures for its purification have been established in our laboratory (5). Therefore, we studied the comparative biochemistry of cytochrome c. Furthermore, as it was found (6) that the chemical entity of housefly cytochrome c does not change during metamorphosis on the basis of its reactivity with cytochrome oxidases, cytochrome c seems to vary very little with environmental conditions. Thus, it may be that the cytochromes c have changed little during evolution except when great changes occurred in the organisms, and that they have retained the properties of the ancestral organisms. In studies on the evolution of organisms, it seems important to classify the organisms roughly. Thus, to study their evolution, it seems to be very valuable to study the comparative biochemistry of organisms in terms of the properties of their cytochromes