48 



Scientific Proceedings (125) 



20 (1980) 



On the nature of the anti-tryptic action of serum and its biologic 



significance. 



By ALBERT A. EPSTEIN 



[From the Department of Physiological Chemistry, Mt. Sinai 

 Hospital, New York City] 



The power which serum possesses to inhibit tryptic digestion 

 is a well known phenomenon, but the nature of the process is not 

 well understood. This is evidenced by the fact that the anti- 

 tryptic power of serum has been variously ascribed to the pro- 

 teins, the lipoids, and the nitrogenous crystalloids of the serum, 

 and more recently to the saponified unsaturated fatty acids 

 present in it. 



The observations to be reported were made in the course of 

 a study begun two years ago on the isolation of the different 

 pancreatic ferments. For reasons which will be discussed at 

 another time, the anti-tryptic action of serum was investigated. 

 At first an inquiry was made into the particular substance in the 

 serum which was endowed with the power to inhibit tryptic 

 digestion. Our results were in conformity with those who 

 found that the albumin fraction of the serum proteins was chiefly 

 responsible for the phenomenon. It may be added that other 

 substances contribute to the total inhibitory action of serum. The 

 globulins, for example, possess the power to a limited degree, 

 and only when present in concentration. While studying this 

 phenomenon with whole serum, in great dilution, it was found 

 that the degree of inhibitory action was proportionate to the 

 quantity of albumin present. Under such conditions other sub- 

 stances apparently, played no part in the reaction. The inhibitory 

 action obtained from the fatty substances present in the serum 

 is insignificant, when contrasted with the remarkable power 

 which whole serum or its albumin fraction possesses. 



The next question investigated was the nature of the inhibitory 

 action. You will recall that when the anti-tryptic action of 

 serum was first observed it was thought to resemble the action of 

 the specific anti-body of the immune system. This view was 

 soon abandoned and the multiplicity of opinions concerning the 



