138 Influence of Low Temperatur es upon Enzymes [March, 



converted protein nitrogen into non-protein nitrogen during the 

 autolysis. The proteolysis was most marked in the frozen wheat 

 seedHngs kept at room temp. for 5 weeks, 48.6 percent of the protein 

 nitrogen becoming non-protein. Microscopic examination showed 

 the absence of bacteria during the autolysis. 



Pepsin. Pozerski (5) exposed a glycerol sol. of pepsin to the 

 temp. of Hquid air (approximately — 191° C.) for 45 min. The 

 enzyme retained ahnost unchanged its power to digest albumin (con- 

 tained in a Mett tube) in the presence of hydrochloric acid. 



Trypsin. Pozerski (5) also exposed an aqueous sol. of trypsin 

 (pancreatin) to the temp. of liquid air (app. — 191° C.) for 45 min. 

 The trypsin retained unaltered its power to digest albumin contained 

 in a Mett tube. 



Rennin. Chanoz and Doyon (6) exposed samples of commer- 

 cial rennet to a temp. of — 180° C, obtained by means of liquid 

 air, for periods of i, 5, 10 and 30 min. These samples coagulated 

 milk with the same speed as did the unfrozen rennet. The curds 

 appeared to be entirely similar. 



Pozerski (5) found that a Solution of rennin, kept for more than 

 I hr. at the temp. of ebullition of liquid air (app. — 191° C), re- 

 tained completely its power to clot milk. 



Thrombin. From the following experiment of Chanoz and 

 Doyon (6), the conclusion may be drawn that thrombin survives 

 exposure to a temp. of — 180° C. Fresh blood of a dog, containing 

 1.5 part of Oxalate per 1000, was kept in liquid air at a temp. of 

 — 180° C. for 13 min. After thawing at ordinary laboratory temp., 

 the blood coagulated upon addition of calcium chlorid, in the same 

 manner as did an unfrozen control sample. 



Zymase. Zymase survives exposure to extremely low temp. 

 Buchner (7) obtained the enzyme by grinding yeast beneath a layer 

 of liquid air. He also prepared zymase by grinding 500 gm. of 

 Berlin bottom yeast S with its own weight of solid carbon dioxid 

 (carbon dioxid snow) for y^ hr. ; the stone-like mass gradually be- 

 coming soft and slightly liquid. The plasma was then obtained 

 from the triturated mass by filtration on a hardened filter with the 

 aid of suction; it fermented sucrose. Zymase also survived com- 

 plete freezing of yeast press-juice, in fact a process for the con- 

 centration of the enzyme was based on that fact. Press-juice, con- 



