32 



TABLE I 



INHIBITION OF PHOSPHOGLYCERALDEHYDE DEHYDROGENASE AND 

 ADENOSINE-TRIPHOSPHATASE BY X RAYS 

 REACTIVATION WITH GLUTATHIONE (added after X irradiation) 



Enzyme 



Phosphoglyceraldehyde 

 Dehydrogenase 



Adenosine-triphosphatase 



X ray Exposure 



100 

 200 



300 

 500 

 100 

 500 

 1000 



Inhibition 



Percent 



21 

 50 

 80 

 94 

 27 

 41 

 73 



Reactivation 



Percent 



Connplete 

 62 



10 

 97 

 56 

 22 



BARRON: Yes. 



PLATZMAN: None was a concentrated solution? 



BARRON: The e 

 solutions containing 14 Mg 



xperiments reported in this table were performed with 

 . per ml., i.e., 1.4x10""^^. 



PLATZMAN: Did you use different concentrations in other experiments'' 



BARRON: Yes. The effect was independent of concentration. That the 

 effect of radiation varies with the different proteins is shown in Table II, where 

 the data on X-ray-induced inhibition of enzyme activity have been assembled: 

 The highest ionic yield was obtained with the -SH enzymes, alcohol dehydrogenase 

 and phosphoglyceraldehyde dehydrogenase, and the lowest with catalase. Not all 

 -SH enzymes, however, have the same ionic yield, because of the different spatial 



TABLE II 

 IONIC YIELDS OF ENZYMES INACTIVATED BY X IRRADIATION 



Enzyme 



Yeast alcohol dehydrogenase 



Phosphoglyceraldehyde dehydrogenase 



Carboxy peptidase 



D-Amino acid oxidase 



Hexokinase 



Ribonuclease 



Trypsin 



Lysozyme 



Catalase 



Ionic Yield 



1 



93 

 18 

 1 



07 

 03 

 0.025 

 0.01 

 0.003 



