1915] Joseph Samuel Hepburn 141 



in birds, whose history prior to freezing was unknown, held for 23 

 months. Aldehyde reductase, which decolorized methylene-blue- 

 formaldehyde sol., occurred in chickens whose history prior to 

 freezing was unknown and which had been in a f reezer for periods 

 of 23 and 63 months. 



According to Pennington, Hepburn, St. John, Witmer, Stafford 

 and Burrell (10), the simple reductase retained its activity as long as 

 28 days in both milk and cream rendered bacteriologically sterile by 

 formaldehyde (o.i percent) and held at 0° C. The aldehyde reduc- 

 tase of the Cream likewise remained active during that period of 

 holding. 



3. Activity of enzymes at low temperatures. Studies have 

 been made of the activity of the following enzymes at low temp. : 

 lipase, diastase, invertase, maltase, zymase, pepsin, trypsin, galactase, 

 urease, rennin. This order will be followed in presenting the data. 

 At times the enzyme studied was permitted to produce autolysis, at 

 times to act in Solution on an artificial medium, at a given low temp. 



Lipase, Kastle and Loevenhart (i) studied the influence of 

 temp. as low as — 10° C. on the lipolysis of ethyl butyrate. For 

 lipase, I cc. each of 10 percent aqueous extracts of liver and pan- 

 creas from a pig were used. In each experiment, this quantity of 

 lipase was permitted to act on 0.23 gm. of the ester, in the presence 

 of toluene as a bactericide, the total volume being 5 cc. After a 

 reaction period of 30 min., the percentage of the ester hydrolyzed 

 by the enzyme was : 



Temp. of the Percentage of ethyl butyrate hydrolyzed by 



Reaction Pancreatic lipase Hepatic lipase 



40° C. 2.82 11.29 



30° C. 3- 16 5.96 



20° C. 2.51 5.27 



10° C. 1.88 3.89 



0° C. 1.25 2.26 



— 10° C. — 0.70 



Richardson (13) ground 150 gm. of perfectly fresh hogpancreas 

 with 500 cc. of water, emulsified with 3 k. of neutral lard, and 

 stored the emulsion at a temp. of — 9° to — 12° C. The pan- 

 creatic lipase caused the initial acidity of 0.25 percent free acid to 

 rise to 2.42 percent after 2 months, and to 4.30 percent after 3 

 months. 



