518 ANNALS NEW YORK ACADEMY OF SCIENCES 



can be regulated by a set of hormones, one of which inhibits, while the 

 other releases the inhibition. All students of endocrinology have long 

 been aware that hormones regulate metabolic processes, and it is not 

 surprising to find in one instance, at any rate, that the regulation oper- 

 ates at the level of the enzyme systems. Houssay and his colleagues 

 in the Argentine have presented cogent evidence that renin, a kidney 

 hormone, is a type of proteolytic enzyme which hydrolyzes one of the 

 plasma proteins to form a pressor substance. In this instance, the 

 hormone regulates metabolic processes by actually assuming an enzy- 

 matic role. 



In still another direction, there has been confirmation that enzymic 

 phenomena underlie essential physiological processes. The brilliant 

 work of Beadle*' and his school have made it abundantly clear that the 

 regulation of growth and development by the hereditary units of the 

 cell, viz., the genes, is exercised through control of enzyme systems. 

 They have shown that each gene determines the synthesis, probably, of 

 a single enzyme. Whereas some of the hormones regulate metabolic 

 reactions by slowing up or speeding up an enzyme reaction, genes 

 regulate by determining the synthesis of an enzyme. Remarkably little 

 is known of the mechanisms by which enzymes are synthesized, but it 

 would appear that, whatever the mechanism, the genie material will be 

 implicated. 



The mere recognition that enzymic phenomena underlie physiological 

 function is, of course, only the first step in the biochemical analysis. 

 Obviously, the exercise of physiological function requires a source of 

 energy, and the energy must arise in enzyme-catalyzed reactions. But 

 how is the energy converted into the manifold forms required by the 

 cell? How is chemical energy converted into mechanical energy of 

 contraction or electrical energy of nervous conduction (to mention 

 two examples) ? There are no transforming elements in the cell, such 

 as the storage battery. Until recently, this problem of energy con- 

 versions was shrouded in deepest fog, but some light has managed to 

 penetrate. It now appears, from the work of various laboratories, that 

 the contraction of the myosin molecule may be coupled with the 

 enzymatic hydrolysis of adenosine triphosphate. The contraction of 

 muscle is now visualized as the integration of the single contractions 

 of myosin molecules arranged in linear series. The picture is, of 

 course, very crude, and probably will be modified by further research. 

 However, if the basic facts are correct, then we have a blueprint for 

 visualizing energy transfers at the enzyme level. Adenosine triphos- 

 phate represents a readily tapped supply of the chemical energy gen- 



