CHEMISTRY. 297 



have regularly used in studies of the activity of this enzyme, the presence 

 of these salts reduced the rate of inactivation to about one-sixth of that 

 observed in their absence. In the presence of the salts about one-sixth of 

 the enzyme activitj^ was lost in 24 hours at 10° C. or in 2 hours at 25° C, 

 and about two-thirds of the enzjane activity was lost in 24 hours at 25° C 

 or in 2 hours at 40° C. 



Although the rate of inactivation is thus greatly reduced by the presence 

 of the salts it is still a very considerable factor with a high temperature 

 coefficient, so that at 40° C. about half of the enzyme was destroyed or in- 

 activated within an hour, even though the solution contained, as has pre- 

 viously been shown, optimum concentrations of chloride, phosphate, and 

 hydrogen ions. All these statements regarding the inactivation of the 

 enzyme in solution hold true for the loss both of its starch-splitting (amylo- 

 clastic) and of its sugar-forming (saccharogenic) activities. The parallelism 

 in loss of these two activities indicates that these two phases in the digestion 

 of starch are not due to two enzymes, but are two stages or phases in the 

 action of one enzyme, and that the inactivation of this enzyme in solution is a 

 process of actual destruction which is greatly accelerated by heat. 



In view of the suggestion made by several writers that the vitamins be 

 classified as enzymes, it is interesting to note that the results, which we have 

 now obtained in the investigation of the heat destruction of the two groups of 

 substances, show temperature coefficients so much higher for typical enzymes 

 than for the water-soluble vitamins as definitely to place the enzj^mes and 

 vitamins in different categories with respect to this important property. As 

 explained in previous reports there is good reason to regard this destruction 

 (or "deterioration") of the enzyme in solution as due to an hydrolysis of the 

 enzyme molecule by the water in which it is dissolved, and the favorable 

 influence of amino-acids as due to the checking of this destructive hydrolysis 

 of the enzyme. All of our results without exception have been consistent with 

 this view; but in one respect the different amino-acids studied have not all 

 yielded exactly identical data. When tested in experiments of 30 minutes' 

 duration at 40° C. in the presence of optimum concentrations of chloride, 

 phosphate, and hydrogen ions, all of the amino-acids showed favorable 

 influence upon the saccharogenic action of the enzyme, while upon the amylo- 

 clastic action a similarly favorable influence was observable in some cases 

 but not in all. 



Tryptophane is typical of the few amino-acids which did not show demon- 

 strably favorable influence upon amyloclastic action within the half-hour 

 of our usual determinations of amyloclastic power. This we interpreted 

 as an indication that the tryptophane radicle is so bound in the enzyme 

 molecule that its liberation occurs only at a relatively advanced stage in the 

 hydrolytic destruction of the enzyme, and hence the addition of tryptophane 

 to the solution in which the enzyme is acting would more readily show its 

 effect in the case of the saccharogenic action which has to do with the later 

 phase of the enzyme's activity. According to this hypothesis, then, a favor- 

 able effect of tryptophane upon amyloclastic action might also be found if 

 tests be made under conditions such as to induce a more extensive destructive 

 hydrolysis of the enzyme, either by exposing the enzyme to the action of the 

 warm water for a longer time or at a higher temperature. This we have now 

 investigated and found to be true. Both when the enzyme is held in water 



