INTRODUCTION 



Certain principles or prejudices in the approach should be clearly stated 

 since these occasionally heretical opinions have been the basis for much of 

 the organization of this volume. 



What is hoped to be pertinent information on the physical and chemical 

 properties of the inhibitors has been given in the belief that the proper use 

 of any inhibitor requires as much knowledge of its properties as possible. 

 Such data are often difficult to find and I am afraid that much important 

 material has been omitted. 



The quantitative formulation of inhibitions has been stressed because 

 here, as in every science, progress often depends on accurate recording and 

 reporting of observations. It is, for example, not only not informative but 

 actually misleading to state that aldehyde oxidase is or is not inhibited 

 by p-mercuribenzoate. What is meant by " inhibited " — 10%, 50%, or 

 100%? What is the concentration of the inhibitor? If it is 0.01 mM it may 

 mean something, but if it is 10 mM probably nothing. What is the source 

 of the enzyme? There are many aldehyde oxidases and they differ quite 

 markedly according to their sources. What substrate and acceptor were 

 used? Is the substrate acetaldehyde, glyceraldehyde, formaldehyde, reti- 

 nene, or even hypoxanthine, and are electron acceptor dyes used or the Og 

 uptake measured? These and other factors must be made explicit. Of 

 course, it is impossible in a book like this to give a complete picture of 

 each inhibition mentioned, but I have tried to state the source of the 

 preparation, the substrate, the inhibitor concentration, and the per cent 

 inhibition in every case, as well as the pH and the incubation times when 

 necessary. 



One can understand a phenomenon better when it can be visualized in 

 some manner and much of the recent work on the inhibition of enzymes 

 has been done with the purpose of clarifying the topography of the en- 

 zyme surface and the nature of the interactions occurring there. Thus I 

 have tried to emphasize the interpretation of data in terms of an accurate 

 delineation of group orientation and intermolecular forces, although in the 

 present state of our knowledge this can seldom be done satisfactorily. 



XV 



