MICHIGAN ACADEMY OF SCIENCE. 
33 
RESISTANCE OF TRYPSIN TO HIGH TEMPERATURES. 
W. E. FORSYTHE. 
Whatever the chemical nature of enzymes may be it is generally ac- 
cepted that they have little resistance to heat. Trypsin is considered 
especially sensitive to such thermal action. 55-60° C is generally con- 
sidered ample to destroy this enzyme when heated in solution. The 
exact point depending very much upon circumstances as, the prepara- 
tion and the technic employed. Vernon (4) and Biernacki (1) put such 
thermal death point for trypsin less than the above while Bayliss & 
Straling (5), Krukenberg (8), and Roeder (8) in general consider such 
temperatures insufficient. 
In this laboratorjq working with three samples of Grubler’s trypsin 
in 5% glass distilled water solutions, heating up to 80°C was usually 
necessary to destroy the trypsin action. This temperature was necessary 
to completely precipitate a proteid that was in these solutions, and thus 
removed from most solutions heated at 80° C or higher. 
The methods employed were various. For temperatures not over 
100°C the best results were obtained if the solution was placed in con- 
stricted and sealed tubes and then completely submerged in water bath. 
Then fresh well washed fibrin flakes were added to these solutions after 
they were put into other tubes and made .3% Na 2 C0 3 . The digestion 
was carried out at 35-37°C and observations made qualitatively from 
time to time. 
PROTECTION BY PROTEIDS AND INORGANIC SALTS. 
In general it is understood that trypsin may be to some extent pro- 
tected from acid, alkalie, and heat destruction when mixed with pro- 
teids, (6), (1), and inorganic salts (1). Schmidt (7) protected water 
solutions against the boiling temperature by heating in the presence of 
peptone, gelatin, and agar. These were among results that caused him 
to indicate the possibility of sterilizing a solution of this enzyme by 
heat. 
Upon the suggestion of Dr. Novy an attempt was made to duplicate 
some of these unusual findings. The results were rather unsatisfactory, 
but the work was limited by an early observation which has since re- 
ceived most attention. 
PROTECTION BY COLD TREATMENT. 
The fact early encountered in the work was the result of irregularities 
in the action of trypsin in solution. It was observed that solutions 
after keeping in the ice box, 0° to 8°C for 24 to 48 hrs. appeared to be 
more resistant to heat than those freshly prepared. As a. result of 
many variously modified tests on these trypsin samples positive diges- 
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