74 The Nature of Biological Diversity 



tyrosines is accomplished by incubating the crystalline aldolase with 

 carboxypeptidase. The results of a typical digestion are shown in 

 Fig. 1. With release of the tyrosines there is a parallel loss of activity, 

 giving rise to a new species which has about 5 per cent of the original 

 activity toward fructose 1,6-diphosphate as a substrate. This change 

 in the aldolase molecule is not accompanied by any discernible change 

 in its size or physical properties. Aldolase, which catalyzes the cleavage 



«- 



& 



Tyrosine 



Or 



Aldolase activity 



-O o 



<D 



3.ol 



o 



2.0 2 



O 



w 



>» 

 I- 



.0 « 

 O 



2 



5^10 30 



Minutes 



60 



FIG. 1. Tyrosine release and activity loss accompanying carboxypeptidase digestion 

 of rabbit muscle aldolase (10). 



of fructose 1,6-diphosphate to 2 triose phosphates, will also catalyze 

 cleavage of fructose 1-phosphate to glyceraldehyde and dihydroxy- 

 acetonephosphate. Surprisingly, the original weak catalytic activity 

 toward fructose 1-phosphate is actually slightly increased after re- 

 moval of the tyrosines. These and other aspects of aldolase action are 

 of keen interest, but take us away from the main thread of our topic. 

 A principal reason for giving the findings on aldolase degradation 

 in this lecture is that they have served as the basis for some interesting 

 comparative studies of aldolase by W. J. Rutter at the University of 

 Illinois. 



