ENZYMES AS SYNTHETIC AGENTS 



I. IN CARBOHYDRATE METABOLISM 



By J. H. PRIESTLEY, B.Sc, F.L.S. 



Professor of Botany, Leeds 



Introduction 



In the present state of our knowledge, the constructive syntheses 

 in the plant that precede the formation of the protoplasmic 

 complex, present a peculiarly difficult problem. 



The activity of organic chemistry has brought to light so 

 many possible compounds and reactions that may form links in 

 the numerous syntheses required, that it is difficult for the 

 biologist to decide what lines best admit of experimental attack. 

 In this quandary it is very desirable that some thread of guid- 

 ance should be obtained through the labyrinth of possibilities, 

 and such a thread is perhaps provided in the idea that the plant 

 may employ enzymes as catalysts to such synthetic chemical 

 reactions. As the number of available enzymes present in an 

 organism is presumably limited and as their powers as a rule 

 seem strictly limited, this narrows the field of inquiry in relation 

 to metabolic synthesis, and it is perhaps worth while considering 

 what light is thrown upon the problem when it is considered 

 from this standpoint. 



Since Croft Hill first announced the synthesis of maltose by 

 the use of the maltase (glucase) extracted from yeast, a number 

 of investigators have experimentally attempted to use enzymes 

 as catalysts to synthetic reactions. The idea underlying these 

 experiments is simple. 



Most of the reactions catalysed by enzymes are of a reversible 

 nature, as is indicated by the way in which the reactions grad- 

 ually slow up and ultimately come to an equilibrium point if the 

 products of the reaction are allowed to accumulate. Thus if 

 a reaction of the general type be expressed by the formula 

 A + B ^tC + D, then the arrows indicate that at any time this 

 reaction is going in either direction and the resultant effect of 

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