274 PLANT PHYSIOLOGY 



beans are used in soap making because of the lipase which they 

 contain, which is used to split the fat preparatory to saponification. 

 It may be added here that Rhine (1926) proposes that fats are 

 often translocated as sugars rather than as fatty acid and glycerin. 



Among the other esterases found in plants is chlorophyllase 

 which synthesizes chlorophyll and also hydrolyzes it. 



Proteases. — Since protein formation and decomposition pro- 

 ceed to some extent in every cell, the proteases are widely dis- 

 tributed in plants. These enzymes are found in greatest abundance, 

 however, in storage regions which are rich in proteins. The pro- 

 teins are not stored in as large amounts as the carbohydrates 

 and fats and, for this reason, proteases in quantities large enough 

 to be easily studied are not commonly found. 



The proteins, which are broken down to amino acids by stages 

 similar to those found in the hydrolysis of starch, are first acted 

 upon by pepsinase to form proteoses or albumoses. These in turn 

 are acted upon by albumase to form peptones, which are then 

 hydrolyzed by peptase to form the amino acids. The amino acids 

 in some cases (especially through the action of bacteria) are 

 broken down still further by amidase into ammonia, skatol, indol, 

 etc. These various steps may be tabulated as follows: 



Substrate Enzyme 



The different products in the chain of protein hydrolysis to 

 amino acids have different reactions by which the exact stage 

 which the hydrolysis has reached may be told. Some of these 

 differences are given in the following table : 



Proteins Proteoses Peptones Amino acids 



Heat effect Coagulated Not coagulated > 



With saturated 



(NH 4 )2S0 4 Precipitated > Not precipitated > 



Biuret reaction Violet Reddish brown > No color 



Alcohol Precipitated > Not precipitated 



Thus if after digestion we find that the product gives a reddish- 

 brown biuret reaction and is precipitated by saturated ammonium 

 sulphate, we may know that digestion has reached the proteose 

 stage only. 



In the animal body, pepsin produced by the stomach reacts 



