further experiments upon the purification of pancreatic amylase.

Abstract

In recent years much light has been thrown upon the chemical nature of some typical enzymes, both by the direct method of purification and analysis and by other methods which, while indirect, have phoven none the less instructive.

Pancreatic amylase has been purified by the methods developed in this laboratory 1 to a maximum enzymic activity practically constant in many independent purification experiments. This material in the dry state is an amorphous white powder having the ultimate composition, and showing the color reactions of typical proteins. Moreover, the enzyme material showed, on analysis by the Van Slyke method, 2 the same forms of nitrogen as are found in typical proteins, and in typical quantitative proportions. Like the purified malt amylase previously described by Osborne, 3 this pancreatic amylase on heating in water yielded a coagulated albumin and left in solution a proteose or peptone.

Our purified pancreatic amylase preparation has much the highest enzymic activity of any material of which we have found adequate record. In thirty minutes at 40°, this material splits 20,000 times its weight of starch and forms 10,000 times its weight of maltose; and notwithstanding its gradual inactivation in solution, this material has, in sufficiently long experiments, digested as much as 4,000,000 times its weight of starch and formed as much as 2,800,000 times its weight of maltose. 4

This great enzymic activity was shown at a dilution of 1 :100,000,000, whereas the most delicate tests for protein are probably not valid at dilutions greater than about 1:100,000. Thus the failure of protein reactions in solutions enzymically active does not show, as many writers assume, that the enzyme is of other than protein nature, since as in this case, the enzymic activity may constitute a test 1000-fold more delicate than any reaction which can be employed as a test for the presence of protein material.