78 



THE FORMATION OF ENZYMES IN BACTERIA 



When the enzyme content of the culture is expressed on a 

 basis of enzyme units per mgrm, dry weight of organism, we find 

 two main types of variation with the age of the culture (Fig. 6). 



In the case of enzymes giving the Type I variation (Fig. 6), 

 cultures taken as early as possible in the growth period have 

 high activities, and these activities decrease as the culture 

 grows, usually falling off rapidly after cell division has ceased. 

 In the Type II variation, cells taken early in the growth period 

 have little or no activity and the enzyme is formed during 

 growth, reaching a maximum at about the time of cessation 



AGE OF CULTURE 



Fig. 6. 



of cell division. After the end of the growth the activity may 

 fall off, due to death of the cells, oxidation or digestion of the 

 enzyme protein, etc. It is probable that we have not yet 

 studied all the types of enzymes present in bacteria and the 

 majority of those so far reported in the literature give a Type II 

 variation with age of culture. These enzymes — deaminases, 

 decarboxylases, dehydrogenases, etc. — are concerned with the 

 breakdown of substrates with the liberation of carbon, nitrogen, 

 energy, etc., and it does not follow that these enzymes have 

 any direct connection with the synthetic processes of growth. 

 Consequently it is possible that this Type II form of variation 



