iQisl Joseph Samuel Hepburn i37 



and aldehyde reductase. This order will be followed in presenting 



the data. 



LiPASE. According to Kastle and Loevenhart ( i ) the lipase of a 

 pig pancreas, which had been held in cold storage at 4° C. f or 7 days, 

 retained 40 percent of its power to produce hydrolysis of ethyl buty- 

 rate. A 10 percent aqueous extract of pig pancreas was held at 

 1° C. for 72 hr., and a 10 percent aqueous extract of pig liver was 

 kept on ice for 48 hr. During holding at these temp., both extracts 

 gained in power to hydrolyze butyric ester, a zymogen having be- 



come activated. 



Pennington and Hepburn (2) demonstrated the presence of active 

 lipase in the crude abdominal fat of chickens of known history, held 

 hard frozen for periods of 12}^, 13, 16, 28, 29 and 4:* months at a 

 temp. of — 9.4° to — 12.2° C, and of chickens, whose history prior 

 to freezing was unknown, kept at that temp. for periods of 54 and 

 89 months. The chickens held for 28 or more months were not 

 marketable and are of scientific interest only. As the period of 

 holding hard frozen grew longer, the activity of the hpase toward 

 esters usually became greater, and the acidity of the crude fat in- 

 creased. Apparently a zymogen became converted into its active 

 form, thus giving rise to increased activity of the lipase. The 

 increase in activity of the lipase, and in the acidity of the crude fat, 

 occurred less rapidly in hard frozen chickens than in birds held at 

 higher temp., e. g., room temp. Active lipase was also found in the 

 crude abdominal fat of a chicken kept at 0° C. for 24 hr. af ter death. 



Pennington and Robertson (3) detected lipase in eggs which 

 had been held at a temp. of 0° C. for 66 days. 



Proteases of plants. Kovchoff (4) demonstrated the power 

 ot these enzymes to survive freezing. Wheat seedlings which had 

 germinated for 17 days, excoriated peas, peas excoriated after ger- 

 mination for 5 days, and certain tissues of the bean, Vicia faha — 

 etiolated caulis tops, etiolated leaves and green leaves — were studied 

 separately. Each sample was frozen for 24 hr., then permitted to 

 undergo autolysis at room temp., in the presence of toluene as a bac- 

 tericide, for a period varying f rom 2 days to 5 weeks. The amounts 

 of protein and non-protein nitrogen were then determined. Almost 

 invariably the former decreased and the latter increased during the 

 autolysis. Therefore, these proteases had survived freezing and had 



