80 F. SORM [5 



quantitative determination of the individual amino acids in the total hydro- 

 lysate was here, as in all other analyses recorded in this paper, carried out 

 by photometric measurement on paper chromatograms by the method of 

 B. Keil,^ Table 3 shows the overall amino acid composition of the arginine 

 peptide fraction isolated from the partial acid hydrolysates of the five serum 

 albumins by means of Amberlite IRA-400. The table reveals marked dif- 

 ferences in the amounts of several of the amino acids, evidently connected 

 with differences in the microstructure of the individual serum albumins. In 

 particular, the conspicuously high threonine content of the peptide fractions 

 obtained from ox and sheep albumin may be noted, as well as the very low 

 tyrosine content of the peptides from duck serum albumin. This last feature 

 is particularly characteristic since all the native proteins contain about the 

 same amount of tyrosine. 



Table 3 



AMINO ACID COMPOSITION OF TOTAL HYDROLYSATES OF THE 

 ARGININE PEPTIDES FROM SOME SERUM ALBUMINS 



Our main concern in the work carried out so far has been with the com- 

 parison of chymotrypsinogen and trypsinogen. These two proteins — both of 

 approximately the same molecular weight — are formed by a single type of 

 pancreatic cell, resemble each other in their enzymic function, and can be 

 obtained crystalline in a state of high purity. In choosing these proteins we 

 further considered that the results of our work might contribute to the 

 determination of their full structures — a problem which will doubtlessly 

 receive considerable attention in the near future. 



The amino acid composition of the two enzymogens as determined in 

 our laboratory is set out in Table 4, which reveals considerable differences 

 between the two proteins in this respect. Chymotrypsinogen contains much 

 less serine than trypsinogen and more threonine and alanine. The Table 



