796 



15. EFFECTS OF VAEIOUS FACTORS ON INHIBITION 



bition decreases with increase in temperature, T^^,, is shifted to higher tem- 

 peratures by the inhibitor, and the Q-^f^ decreases with rising temperature 

 in all cases but faster when the inhibitor is present (Fig. 15-14). The // val- 

 ues are increased by quinine, particularly in the lower temperature range, 

 giving rise to a discontinuity in the curves which is not present in the case 



200 



100 



0.5 



Fig. 15-14. Effects of temperature on the inhibition of horse 



serum chohnesterase by quinine plotted in four different ways. 



In all cases, the quinine concentrations are: A, 0.025 m.M; B, 



0.05 mif; and C, O.I mi¥. (From Robert et al, 1951.) 



of the uninhibited enzyme (Table 15-1). It is interesting to speculate if 

 this critical temperature is related to a temperature-sensitive active center 

 flexibility. Both quinine and lower temperatures may reduce the flexibility 

 and hence the efficiency of the catalysis. However, the situation may well 

 be more complex than this, as indicated by the reversal of some of the ef- 



