298 CARNEGIE INSTITUTION OF WASHINGTON. 



for a longer time at 40°, and when it is so exposed for even a short time at 50°, 

 the favorable influence of the tryptophane upon the amyloclastic as well as 

 the saccharogenic activity of the enzyme becomes clearly demonstrable. 



In a parallel series of experiments, carried out during the year in this 

 laboratory without financial aid from the Institution, but in close coordination 

 with its work, we have found that the rate of destruction of pancreatic amy- 

 lase is 30 times as great at 50° as at 40°. 



Hence we had reason to expect that if our theory is correct the favorable 

 influence of the tryptophane in conserving the enzyme would be measurable 

 even in relatively short periods of time at the higher temperature, and in fact 

 we found that when thus tested in the solution of a highly purified pancreatic 

 amylase the tryptophane reduced by about one-third the loss of activity 

 shown by the enzyme when held in solution at 50° C. for 15 minutes. 



In connection with these studies we have investigated the optimum hydro- 

 gen-ion concentration for the activity of pancreatic amylase at temperatures 

 ranging from 30° to 60°, and for digestion periods from half an hour to 2 hours, 

 and have found that throughout this entire range of time and temperature the 

 greatest activity, both amyloclastic and saccharogenic, is shown at the opti- 

 mum which we had previously established for digestions of 30 minutes at 

 40° (pH = 6.7 to 7.2). In order to determine whether this is a relationship 

 of general application, a similar study of malt amylase is now being made. 



The work of the past year, together with that of the years preceding, has 

 therefore thrown light upon the chemical nature of pancreatic amylase (and 

 to a less extent upon that of malt amylase and of pancreatic protease also) 

 from three different angles: (1) the preparation of the enzymes in the form 

 of highly purified products and the direct analysis of these products with 

 reference to their ultimate and proximate composition, physical properties, 

 and behavior toward chemical tests; (2) the comparative effects of different 

 antiseptics, those characterized by their chemical action upon proteins 

 being found very much more destructive than those of the lipoid-dissolving 

 type; (3) the destructive action of warm water upon the enzyme and the 

 effects of amino-acids in retarding this destruction. The data of these three 

 lines of evidence are entirely consistent and all point to the protein nature 

 of the enzyme. 



This work upon the chemical nature of the amylases and related enzymes 

 is now being extended; and studies of their enzymic activity and physico- 

 chemical behavior, planned in the light of newer knowledge of their chemical 

 nature which we have gained through the work of the past few years, are now 

 being undertaken. 



The efficient collaboration of those who have shared in these investiga- 

 tions, whether as research assistants or volunteers, is gratefully acknowledged. 



Smith, Edgar F., University of Pennsylvania, Philadelphia, Pennsylvania. 

 Continuation of the study of the sodium tungstates. (For previous 

 reports see Year Books No. 16, 17, 21.) 



The study of the sodium tungstates has been continued during the year. 

 One paper has been published. In it the methods for preparing the 4 : 10 

 salt have been carefully reviewed and a new method for its preparation 

 described. 



