G. ROBERT GREENBERG 



Figure 1. Actually the specific activity (and therefore the C^* 

 activity) of the IMP passes through a rise and fall curve typical 

 of a precursor-product relationship (32). When higher concen- 

 trations of IMP were added to the system and the phosphatase 

 was saturated, the rate of conversion of IMP to hypoxanthine 

 could be increased by about 10 times over that observed dur- 

 ing de novo synthesis. 



3.0-1 



T 



20 40 



TIME, MINUTES 



Fig. 1 . Constancy of an intermediate compound in a steady-state synthesis. 



It is apparent from the discussion above that in a sequence 

 of enzyme reactions the step with the lowest velocity at saturation 

 with its substrate may not be the limiting reaction in the steady 

 state. Under such conditions, another enzyme may become 

 limiting. 



SOME ASPECTS 

 SYSTEMS 



OF THE PURIFICATION OF MULTI-ENZYME 



Eventually it becomes necessary to fractionate the crude 

 extract in order to isolate intermediate reactants. To discuss 



548 



