ACT10X Or THI-: /<.\/V.1//>\ Hi 



for some time without injury, according to TAYLOR'S obser- 

 vations. The presence of oven a small amount of water 

 soon makes the highest temperature that this lipase can 

 \\ithstand fall far below the boiling -point. 



Quantitative studies show that the activity of lipase is as 

 dependent upon external conditions as is the activity of other 

 enzymes. An increase in the concentration of the lipase in 

 a reaction mixture is followed by an increase in the velocity 

 of the cleavage of the fat. but by no means in proportion to 

 the amount of lipase added. 



The amount of fat split in a reaction mixture under the 

 inlluence of lipase increases with the time, but becomes less 

 in each succeeding unit of time. All the fat is never split, 

 even when infinite time is allowed, owing to the fact that 

 the activity of this ferment is reversible. 



Lipase is exceedingly sensitive toward acids, losing its 

 activity, for example, in a very few minutes in a hydrochloric- 

 acid solution having the concentration of the acid in the 

 stomach. At the height, of digestion the lipase found in the 

 stomach can therefore have but little or no effect upon* the 

 fats of the food. Lipase acts best in a neutral orslightly 

 alkaline medium. Its activity is markedly red ucc^p done 

 away with entirely through the presence of various Setttral 

 salts. 



That the activity of lipase is reversible was demonstrated 

 in this country by KASTLE and LOEVENHART, 1 and independ- 

 ently of them b HANiuoT 2 in France. KASTLE and LOEVEN- 

 n AH r were able to show that if lipase is added to ethyl butyrate 

 this is split into ethyl alcohol ami butyric acid. The re- 

 action is, however, incomplete. If, on the other hand, lipase 

 is a tided t-o a mixture of ethyl alcohol and butyric acid, ethyl 

 but yra te is synthesized. 



This may be illustrated by the following experiment: 



1 KASTI,K and LOEVENHART: American Chcm. Jour., 1900, XXIV, 

 p. 491. 



2 HANRIOT: Compi . rorni. Soc. biol., 1901, LIII, p. 70. 



