ENZYMES ATTACKING NUCLEIC ACIDS 



561 



Fig. 2. Probable structure of ribose phosphate poljsaccharide of Hemophilus 

 influenzae. (From Zamenhof et al.^^] 



H-C- 



H-C-OH 



1 

 H-C-0 



H-C 



Hj-C-OH 



0- 



I 



in 

 o 



Py (or Pu) 



H-C 



I 

 H-C-OH 



H-C-0 



H-C- 



•O-C-H2 



0- 







Step 1 



Transphosphorylation 



Py 



H2-C-0H 



Py (or Pu) 

 H-C 



H,-C-OH 



Py (or Pu) 

 H-C 



H-C-OH 



+ H2O Step II 



Hydrolysis 



H-C-0 



P=0 H-C 



0- H2-C-OH 



Fig. 3. Mechanism of action of ribonuclease I according to Brown and Todd. 



