CHEMISTRY. 357 



by total nitrogen, amino nitrogen, or acidity of digestion products, 

 by increased conductivity of substrate solution, or by the polarimetric 

 method, the best pancreatic amylase preparations show a strikingly 

 high and consistent proteolytic activity of the tryptic type, fully 

 equal in fact to that of the most active conunercial trypsin which has 

 come to our notice, though not so high as in certain pancreatic enzyme 

 preparations made in the laboratory. Our best malt amylase prep- 

 arations show no proteolytic activity, although tested through a 

 wide range of hydrogen ion concentrations. This and the fact that 

 the optimum amylolytic and proteolytic activities of malt extract 

 are shown at different degrees of acidity are consistent with the general 

 view that malt amylase and malt protease are independent substances, 

 whereas in the case of purified pancreatic amylase we have the two 

 enzymic activities concentrated in the same product and showing 

 optimum activity at nearly the same degree of alkalinity. These 

 results, which are now ready for publication, give added weight to 

 the problem of the exact nature of the relationship which exists 

 between the amylolytic and proteolytic properties of our purified 

 amylase preparations, upon which it is hoped that further light may be 

 obtained through purification experiments directed to the concentra- 

 tion of proteolytic power. 



The course of the hydrolysis of starch to maltose under the influence 

 of purified malt amylase has been studied, with quantitative deter- 

 minations of the velocity constant at different stages of the hydrolysis 

 and under varying conditions of activation and concentration. In 

 some cases the experiments have been performed on different starch 

 substrates — the soluble starch ordinarily used, starch pastes prepared 

 by heating in the autoclave, and the a and /3 fractions of starch as 

 separated by the method recently developed in this laboratory. In 

 this connection it has been found that the "delayed iodine end-point," 

 previously noted as a difficulty encountered in studying the amylo- 

 clastic action of purified malt amylase upon soluble starch, occurs 

 also with each of the new substrates and is therefore to be regarded 

 not so much as a defect of the method but rather as a characteristic 

 property of this enzyme. The comparison of the different starch 

 preparations as substrates also shows that soluble starch is well 

 adapted to this purpose and that its use leads to conservative esti- 

 mates of the diastatic powers of purified amylase preparations. 



The experiments upon the purification of the amylase of Aspergillus 

 oryzce and the comparison of its chemical properties with those of 

 pancreatic and malt amylases are being continued. 



The efficient work of those who have collaborated in these investi- 

 gations, whether as research assistants or volunteers, is gratefully 

 acknowledged. 



