EFRAIM RACKER 



Structure and biological activity. As "kineticist," he will study 

 the process of substrate activation; he will explore the con- 

 ditions governing the efficiency of catalytic performance; and 

 he will derive equations compatible with his data which might 

 give him clues to the mechanism of enzyme action. As a 

 progressive enzyme "reactionist," he will use the enzyme as a 

 stoichiometric reactant ; he will explore the active center of the 

 enzyme and the points of enzyme-substrate interaction. 



Some of these investigations require rather large quantities 

 of highly purified enzymes, and it is not surprising that those 

 enzymes which are readily available in large amounts have been 

 studied most extensively. For example, crystalline glyceralde- 

 hyde-3-phosphate dehydrogenase (TDH) can be prepared in 

 gram quantities either from rabbit muscle or from yeast in the 

 course of a few days. During the past years it has become 

 the subject of study in numerous laboratories all over the world. 

 Since these studies have been conducted with a relatively pure 

 protein, and because of the multifunctional activities of TDH, 

 this enzyme will be frequently cited as an example in the 

 following pages. 



Enzymes as Proteins 



The biosynthesis of proteins, their molecular structure, and 

 the relationship of structure to biological activity are among the 

 unsolved and most challenging problems in biochemistry. 

 Enzymes are particularly suited for such studies because their 

 biological activity can be rapidly and accurately determined by 

 very sensitive methods. The specificity of these methods permits 

 the detection of a particular enzyme in a mass of other proteins. 

 It was possible in this way to detect the formation of new enzyme 

 proteins in cell-free systems, although little increment in total 

 protein nitrogen had occurred (10). 



Studies on the composition and sequence of amino acids of 

 various enzymes having the same action but obtained from 

 different sources may represent the beginning of a new kind of 

 comparative biochemistry. A remarkable similarity in amino 



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