XVI INTKODUCTION 



Metabolism within cells is almost always a matter of multienzyme sys- 

 tems and so the effects of inhibitors on such systems have been discussed 

 fully wherever possible, although this is even more difficult to describe 

 quantitatively than the behavior of single enzymes. 



The importance of the specificity of inhibition was sufficiently emphasiz- 

 ed in the previous volume and it should be clear that this is a critical prob- 

 lem which has been neglected, ignored, or abused extensively. It is not 

 an easy matter to evaluate the specificity of an inhibitor under various 

 conditions, particularly when the necessary data are lacking, but it is 

 hoped that at least a provisional picture has been presented in some in- 

 stances. 



Certain aspects of metabolism (e.g. glucose utilization, respiration, pho- 

 tosynthesis, protein synthesis, or oxidative phosphorylation) and cellular 

 activity (e.g. active transport, membrane potentials, movement, mitosis, 

 or proliferation) are obviously of general significance, and the effects of 

 inhibitors on these have been emphasized. This is not to say that other 

 pathways or functions are unimportant, and indeed where necessary they 

 have been treated as adequately as possible, but one cannot discuss all 

 the actions of each inhibitor, so that some compromises must be made. 



A major use of inhibitors is in the attempt to correlate cellular functions 

 with particular enzymes or metabolic pathways, and for this reason, as 

 well as the fact that this represents one of the most fascinating aspects of 

 inhibitor study, these correlations have been discussed fully if the infor- 

 mation has been available, and the effects on certain organisms or processes 

 have often been given in the hope that some correlation will emerge or 

 further work will be stimulated. It is believed that conceiving inhibitor 

 actions in terms of deviations in the energy flow is of some value although 

 an accurate formulation of this must await the development of a new 

 terminology. 



It is simpler to restrict the treatment of an inhibitor's action to a par- 

 ticular organism or tissue, but it is felt that a great deal may be learned 

 from comparative inhibitor enzymology. Therefore, in the tables, the ef- 

 fort has been made to present the results from as many sources as possible 

 for a particular enzyme or metabolic pathway since by doing this one is 

 better able to see the great extent of the variability in responses; only a 

 distorted view is obtained if a limited range of action is considered. 



Paradoxical actions have been both the despair and delight of scientists 

 in many fields, and it is recognized that, some of our finest theories have 

 originated in the observation and study of anomalies. There is an inherent 

 desire in most of us to eliminate anomalies and perhaps devote a good deal 



