74 



THE FORMATION OF ENZYMES IN BACTERIA 



hydrogenase. In this example the optimum activity plcL is 

 6-0 (Fig. 46), but maximal formation of the enzyme occurs 

 at ^H 8-0 (Fig. 4a) and investigation of the effective activity 

 between growth pH values of 6 and 8 shows that the greater 

 formation of the enzyme between these values compensates 

 for the loss of activity per enzyme unit over this range. 

 As a result the effective activity is approximately constant 

 over the middle of the growth range but falls off rapidly 



GROWTH 

 pH-d 



Qme 



20- 



45 5 6 7 8 9 



pH OF MEDIUM DURING GROWTH REACTION^H 



(O) (b) 



Fig. 4. (a) Variation of potential activity (•-•) and effective 

 activity (x---x) of hydrogenase of Esch. coli with ^H of 

 medium during growth. 

 (6) Variation of reaction pH of hydrogenase activity of Esch. coli 

 grown at various pB. values. (After Gale and Epps, Biochem. 

 J., 1942, 36, p. 612.) 



outside these limits. In these cases, then, we get a restricted 

 amount of compensatory formation over the neutral part of 

 the growth range but no compensation towards the ends of 

 that range. Enzymes in this group include hydrogenase, 

 succinic dehydrogenase, glucozymase, and tryptophanase. 



Growth temperature 



It has become customary to study many organisms after 

 growth at 37° C, presumably since this is the temperature of 



