EFFECTS OF TEMPERATUEE: CELLULAR SYSTEMS 787 



experimentally to distinguish between ordinary enzyme inhibition and 

 denaturation of the enzyme by the inhibitor. If the depression of the ac- 

 tivity is reversible by some means, the proponents of the theory of denatu- 

 ration would say that the denaturation is reversible. Inasmuch as combi- 

 nation of the inhibitor with the active center of the enzyme is sufficient for 

 inhibition, it is apparent that the burden of proof for the occurrence of 

 denaturation is on those who propose it is an important factor. 



The inhibitions of bacterial luminescence by sulfanilamide and urethane 

 show quite different temperature characteristics (Johnson et cd., 1943). 

 The inhibitions observed in Vibrio phosphorescens and Photohacterium 

 pJiosplwreum are plotted in Fig. 15-10 (the data may be found in Table 



20° 25° 30° 35' 



Fig. 1.5-10. Effects of temperature on the inhibitions of bacterial kiminescence 



by sulfanilamide (X) and urethane (O). The solid curves are for V . pliosphorescens 



and the dashed curves for P. phosphoreum. Concentrations: sulfanilamide 3 mM 



and urethane 150 miVf. (From Johnson et al., 1943.) 



10-1) and it is evident that sulfanilamide inhibition falls and urethane 

 inhibition rises with an increase in the temperature. Furthermore, the 

 Topi for luminescence is shifted upward by sulfanilamide and downward 

 by urethane (Johnson et al., 1945). Urethane at 300 mM shifts the T„pi 

 from 32° to IJo in V. phosphorescens and from 23° to 17^ in P. phosphoreum 



