570 



B. A. RUBIN 



Table 2 



The influence of the environmental conditions on the 

 activity of cytochrome oxidase 



(average findings after Verzhbinskaya) 



Different classes of organism diflfer from one another, not only in the activity 

 of their cjlochrome oxidase, but also in its 'quality' which is expressed in an 

 alteration in the dependence of the activity of the enzyme on temperattire and 

 partial pressure of oxygen. 



A considerably higher temperature coefficient is characteristic of the cyto- 

 chrome oxidase of terrestrial animals. The respiratory requirement of these 

 animals increases markedly in oxygen. 



It is well known that, in parallel with the increase in the complexit}' of the 

 structure of the organism of animals, there occurred a stabilization of the con- 

 dition of the environment of the internal tissues. Thus, mammals, which have 

 highly developed nervous and blood-vascular systems, are characterized by 

 constant body temperature and by the respiring cells being maintained at a 

 constant partial pressure of oxygen. At the same time, one may note a certain 

 simplification of the oxidative enzymic systems. Thus, in higher animals, espe- 

 cially in such speciaHzed tissues as the brain and skeletal muscles, the pre- 

 dominant role in aerobic oxidation falls on the cytochrome system. It is inter- 

 esting that, even within the confines of an animal organism, the individual organs 

 and tissues, which are subject to specific conditions, possess certain pecuharities 

 in the course of their oxido-reductive processes. As an example we may adduce 

 the crystalline lens of the eye, which has no blood vessels. It is not cytochrome 

 oxidase which plays the predominant part in the respiration of this tissue, but 

 the direct oxidation of glucose [i]. 



From the evidence which has been brought forward it follows that the pre- 

 sence in green plants of complicated systems of oxidases made up of many 

 components may be regarded as an important adaptive property which corres- 

 ponds with the specific pecuharities of the structure of these organisms and the 

 conditions of the medium in which they are accustomed to carry out their vital 

 activities. To these pecularitics one must, to a certain degree, attribute the ability 

 of green plants to exist under conditions of continually varj'ing temperature, 

 illumination, moisture etc. 



I 



