286 UNITY AND DIVERSITY IN BIOCHEMISTRY 



resulting consumption of inorganic phosphate brings about a decrease in 

 the intensity of glycolysis, and inversely. The Pasteur Effect is therefore an 

 example of an autoregulation of all the complex phenomena of the priming 

 reactions. Another factor in the regulation of the intensity of respiratory 

 metabolism is operative in the mitochondria, and this is the supply to the 

 interior of the mitochondria of phosphate acceptors such as AMP and ADP. 

 To the autoregulatory processes of this type can be added the action of 

 specialized regulators such as the hormones which have been developed 

 by organisms in the course of biochemical evolution. 



III. THE GENETIC CONTROL OF THE RELATIVE 

 RATES OF ENZYMATIC REACTIONS 



Although it is true that the cells of various organisms all possess meta- 

 bolic systems having the general features described in part three of this 

 book, each species has certain specific peculiarities in the macromolecules 

 of which it is formed, the enzymes included. 



Heredity transmits to the descendants of an organism the specific type 

 of control of the relative rates of the diverse enzymic reactions which take 

 place in each of its cells. It has now been well established that an alteration 

 in a given gene can bring about definite biochemical changes manifested 

 by the disappearance of one constituent in the organism, or the appearance 

 of a new one, or by an increase or a decrease in the amount of a compound 

 or of a group of compounds. New stationary states are set up resulting from, 

 changes in the speed of this or that metabolic process. For example, in a 

 given organism consider the concentration of a substance A. In the station- 

 ary state in the organism, the concentration of A remains approximately 

 constant as a result of an equilibrium between the production process and 

 its transformation. If the rate of production decreases, even slightly, and if 

 the rate of transformation does not alter, then substance A will disappear. 



Although the biochemical phenotype, like phenotypes in general, is a 

 product of the interaction of the internal milieu of the cell, and its genotype, 

 the means by which the latter influences the system of macromolecules in 

 the cell and in particular the enzymes still remains a mystery. 



REFERENCES 

 HoLZER (1953). Tiber Fermentketten und ihre Bedeutung fiir die Regulation des 



KohlenhydratstoflFwechsels in lebenden Zellen. Biologic und Wirkung der 



Fermente. 4. Colloquium der Ges. fiir physiol. Chem., Springer, Berlin- 



Gottingen-Heidelberg. 89-112. 

 Lardy, H. A. (1952). The role of phosphate in metabolic control mechanisms. 



The Biology of Phosphorus, Wolterink, L. F. (Editor) Michigan State College 



Press, 131-147. 

 Potter, Van R. (1949). The control of metabolism. Respiratory Enzymes, L,ardy^ 



H. A. (Editor) Burgess, Minneapolis, revised ed., 264—272. 



