VARIATION OF INTRACELLULAR INHIBITION WITH pH 



745 



of enzyme or product becomes available, the process will begin to operate, 

 and as the pH^ is further increased the enzyme concentration rises rapidly, 

 so that the inhibition on the measured process falls precipitously. From a 

 more general standpoint, the existence of critical thresholds in cell me- 

 tabolism must be accepted. Up to a certain point the coordinated reactions 



1.00 



0.80- 



0.60- 



0.40- 



0.20- 



FiG. 14-29. Variation of the inhibition of bioluminescence in 



Achromobacter by 2-methyl-l,4-napthoquinone with the pH. 



(From McElroy and Kipnis, 1947.) 



can maintain their functional relationship, but beyond this point the system 

 may not only cease to operate but may also disintegrate in the sense of 

 losing irreversibly its organization or necessary components. Cyclical or 

 regenerative systems are especially prone to show such critical operation 

 levels. 



