LEIGH E. CHADWICK 55 



To derive useful generalizations from these scattered observations con- 

 cerning the effect of temperature on ChE inhibition is difficult. We are 

 clearly confronted with processes of several different types, and for none 

 of them do we have really adequate information. Certain non-competitive 

 inhibitors are evidently denaturants at high concentrations. Apparently 

 they act in some different, though wholly unexplained, manner when pres- 

 ent in lower concentration. Parallels for this situation have been discussed 

 by Johnson et al. (25). The competitive inhibitors, on the other hand, give 

 results that, in their general form and in their variety, point to the same 

 complexities that are seen in the reaction of the enzyme with substrates. 

 This was perhaps to be expected, since competitive inhibitors are pre- 

 sumably combining with the protein in the same manner and at the same 

 sites as the substrate. One judges that considerably more work must be 

 done with a greater variety of inhibitors and ChE's before we shall be 

 able to draw valid general conclusions about the effect of temperature on 

 these various inhibitory processes. 



CONCLUSION 



This review reveals first of all how incomplete our information is in all 

 three of the areas considered. As yet, experiments on the temperature de- 

 pendence of ChE activity have not covered enough ground to contribute 

 greatly to our understanding of the nature of this group of enzymes and 

 of their reactions with substrates and inhibitors. Partial though our knowl- 

 edge still is, it is nevertheless sufficient to throw into relief the fact that 

 the reactions concerned in the three types of process discussed are in each 

 case less simple than is generally taken for granted. Though it was by 

 varying the temperature at which the experiments were done that these 

 complexities were brought into the foreground, this does not imply that 

 the complicating factors are absent or negligible when temperature is kept 

 constant, although that is the tacit assumption of many workers. Thus 

 the temperature data may even now serve the useful purpose of cautioning 

 one against adopting an oversimplified view of the preparations that are 

 ordinarily used in kinetic studies with ChE's. 



Superficially regarded, these disturbing factors may seem merely an 

 annoying obstacle to our understanding of the system, or a distraction 

 tending to draw our attention away from the primary goal of our enquiry ; 

 l)ut they should more properly be welcomed as affording added opportu- 

 nities for probing the heart of the problem. We shall not explain these 

 anomalies without in the process learning something significant about ChE 

 itself. 



The bibliography to follow does not contain one single reference in which 

 the temperature response of ChE has been studied in a living organism. 

 This is a deplorable admission from an entomologist who has himself done 



