340 CARNEGIE INSTITUTION OF WASHINGTON. 



influence of the amino acid may be due, at least in part, to a further 

 protection of the enzyme from deterioration in the aqueous dispersions 

 in which it acts. This we have found to be the case, solutions of pan- 

 creatic amylase which had stood for one hour at 40° showing about 

 one-third greater amylase activity when alanine had been added to 

 the solution in advance. The conditions in this case were such as to 

 result in greater deterioration than in our ordinary tests of enzyme ac- 

 tivity, both because of longer heating and because of the absence 

 of substrate. 



A somewhat extended series of quantitative experiments will be re- 

 quired to determine to just what extent the favorable influence of amino 

 acids upon the activity of amylases is due to protection of these from 

 deterioration. Meantime, the present demonstration that the presence 

 of amino acids does retard deterioration of the enzyme constitutes an 

 interesting addition to the evidence supporting the view that the 

 enzyme itself is a substance of protein nature or which contains pro- 

 tein as an essential constituent. 



We have also found that amino acid may be strikingly effective in 

 protecting the enzyme from the deleterious action of an inhibitory 

 agent, such as copper. Thus a pancreatic amylase solution lost 80 

 per cent of its enzymic activity when copper sulphate was added to the 

 extent of a concentration of 0.00003 molar; but the presence of 0.1 per 

 cent amino acid prevented the inhibition of the enzyme by the copper 

 and resulted in an increase of enzyme activity almost as great as would 

 have been effected by the amino acid in the absence of copper. 



In addition to protecting the enzyme from gradual deterioration 

 under the influence of the water in which it is dispersed, or from inhi- 

 bition by certain actively deleterious substances if present, amino acids 

 may or may not literally activate the enzymic hydrolysis by directly 

 facilitating or accelerating the interaction of enzyme and substrate, 

 or they may function by sustaining the activity of the enzyme through 

 combining with some product or products of the enzyme action, which 

 products might otherwise combine with the enzyme itself, thus reducing 

 its activity, or might if remaining free in the solution tend to bring the 

 hydrolysis to equilibrium. Experiments designed to throw further 

 Hght upon these points are now in progress. 



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

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

 acknowledged. We desire also to thank Dr. Davenport and Dr. Riddle 

 of the Station for Experimental Evolution for the alanine used in our 

 experiments. 



