560 



G. SCHMIDT 



Acid extract 

 of beef pancreas 



Trypsin 



Precipitate 

 Trypsinogen 



Compound 



*^ >!^i^ trypsin* 



'. a t€ n inhibitor 



4 



^^.t?, 



Trypsin 

 inhibitor 





Ribonuclease 



01 



0.2 



-0,3 



04- 



-05 



-0.6 



Desoxy- 

 nbonuclecse 



Chymo - cc- Chyjno- 



trypsinogen trypsin 



-0.7 



0.8 



09 



Saturation of 

 ammonium sulfate 



0-Chymo- 

 tpypsin 



if"- Chymo - 

 trypsin 



Fig. 1. Fractionation of pancreas enzj^mes. [From. M. Kunitz.'*] 



model substrates for other phosphodiesterases, are resistant against ribo- 

 nuclease.^® 



Hydrolysis Products Resulting from the Action of Rihonuclease I on Ribo- 

 nucleic Acids. Ribonuclease I does not hydrolyze all bonds between the 

 component nucleotides of ribonucleic acid, but it catalyzes the cleavage 

 only of certain strictly defined internucleotide bonds, namely those be- 

 tween the 3'-pyrimidine nucleoside phosphoryl groups and the 5 '-hydroxy 

 groups of the adjacent purine or pyrimidine nucleotide groups.^* '^^^ 

 Thus, neither the bonds between adjacent purine nucleotide groups nor 



16 G. Schmidt, R. Cubiles, N. Zollner, L. Hecht, N. Strickler, K. Seraidarian, M. 



Seraidarian, and S. J. Thannhauser, /. Biol. Cheni. 192, 715 (1951). 

 !«• H. S. Loring, F. H. Carpenter, and P. M. Roll, /. Biol. Chem. 169, 601 (1947). 



