Enzymes from various animal sources responsible for amylolytic activity as measured by a precise viscosimetric method have been investigated with regard to individual characteristics in relation to enzyme source. The principal criteria have been the course of spontaneous inactivation of preparations from different sources alone and in mixtures, and comparison of variations of relative activity with change in pH.

It is strongly indicated that the observed amylolytic activity of hog pancreatin, and that of the serum of a depancreatized dog are attributable to single chemical individuals, while that of human saliva is caused principally if not entirely by a single individual, which appears to be subject to reversible dissociation.

These three individuals are clearly distinguishable from each other.

The amylolytic activity of dog pancreatic extract is due to the same individual found in the serum of a depancreatized dog, while that of human pancreatic extract and of human serum are due to the same chemical individual found in human saliva. Thus it may be said of the amylases studied, that specificity depended upon species source rather than organ source.

Evidence of similar variations in activity with change in pH and equal sensitivity to ultraviolet light furnish strong indication that hog and human amylases have a common amylolytic radical.

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