Oxidation Systems of Organisms 



569 



From the sketch which has been given above, which is far from being complete, 

 it follows that in higher plants the oxidase enzymic system is constructed on the 

 principle of multiphcity. 



It is interesting to supplement the evidence from higher plants with material 

 characterizing the oxidative system of animal organisms. What strikes the eye 

 when one does so is the lack of uniformity of the pictures which are presented 

 by different representatives of the animal world. 



Those which are closest in this respect to the higher plants are those forms of 

 animal which have not got a well developed blood-circulatory system or a con- 

 stant body temperature. The systems catalysing the terminal stage of respiration 

 in these organisms are also characterized by a multiplicity of components and 

 a high lability, that is, they are inconstant. Thus, the respiration of the grass- 

 hopper embryo during the diapause is completely resistant to cyanide, while, 

 in other phases of development, a considerable part of the respiration is sup- 

 pressed by respiratory poisons [21]. Tyrosinase has been observed in the maggots 

 of flies, in crustaceans, in molluscs and other animals. The blood of the crab. 

 Cancer pagarus, contains a copper-containing protein with the properties of a 

 pseudophenolase of the same type as catechol oxidase. In the prepupal and pupal 

 stages of development of the meat fly there is a considerable rise in tyrosinase 

 activity alongside a fall in the significance of cytochrome oxidase [22]. It is 

 interesting that cytochrome oxidase has been shown to be present in the brains 

 of all aquatic, cold-blooded vertebrates and some amphibia although cytochrome 

 is practically absent from them, this being associated with a negligibly small 

 activity in these animals of the cytochrome system as a whole [23, 24]. The 

 formation of the fiill (true) cytochrome system in the brain cells is associated 

 with a later stage in evolution. Most probably it was conditioned by the tran- 

 sition of animals to a terrestrial way of life. 



At this time there occurred a diminution in the part played by anaerobic oxi- 

 dative processes which were responsible for a substantial part of the energy 

 metaboHsm of the brain in aquatic vertebrates, which developed under condi- 

 tions in which oxygen was hard to obtain [25] (Tables i and 2). 



Table i 



Respiration, anaerobic glycolysis and cytochrome oxidase 



in the brains of vertebrates 



(average findings at 37 • 5 C after Verzhbinskaya) 



I 



