ANTI-ENZYME IMMUNITY 255 



hydrolysis of casein or gelatin was completely absent in the reaction 

 mixtures containing the substrate and the supernatant which was 

 obtained by centrifuging off the papain-antipapain precipitates. In 

 the reaction mixtures containing the papain-antipapain precipitates 

 the inhibition of the hydrolysis of casein at the end of 1 8 and 42 hour 

 periods was, respectively, 72.5 and 58 per cent; similarly the inhibition 

 of the hydrolysis of gelatin at the end of 20 and 24 hour periods was, 

 respectively, 71.5 and 72.6 per cent. In view of the difference in the 

 degree of inhibition of the hydrolysis of casein or gelatin arising from 

 the difference in the details of the two methods employed, it would 

 appear that when the papain-antipapain precipitate is left in the 

 reaction mixture a certain degree of dissociation may have taken place. 

 Under these conditions the substrates may have competed with the 

 antibody for the active group (or the combining site) of the antigen 

 causing partial displacement of antibody and thus reducing the degree 

 of inhibition from 100 to ca. 70 per cent. An alternative explanation, of 

 course, would be that combination of papain with antibody blocks the 

 enzymatically active groupings only up to about 70 per cent of maximal 

 activity. 



e. Antibody Against the Proteolytic Activity of Snake Venom. 

 Githens (1941) reported the result of a study of the proteolytic activ- 

 ities of snake venoms from 26 species. Using gelatin as substrate 

 he found that there was no significant difference in the speed of diges- 

 tion by different venoms, and the comparison of different lots of 

 venoms of the same species showed close agreement, but he observed 

 that venoms of different species of pit viper show great differences. In 

 studies on the antiproteolytic property of antivenins Githens found 

 that 0.3 ml. of antivenin prevented the proteolytic effect of as much as 

 1 mg. of some snake venoms, and was entirely ineffective and irregular 

 with others. Both crotalidic and cascabel antivenins showed stronger 

 action against the venoms of a true viper, the daboia, and of an elopine 

 snake, and the Australian tiger snake, than against those of many pit 

 vipers. Eagle (1937, 1939) studied the proteolytic activity of venoms 

 using gelatin as substrate. Comparing plasma clotting and gelatin 

 digesting activities of certain venoms, he found that the venoms 

 arranged in order of their gelatin-splitting activity showed also pro- 

 portional clotting activity. When the proteolytic activity of certain 

 venoms was found to be below a certain level they also failed to mani- 



