128 BIOLOGICAL CHEMISTRY 



tryptic digestion the amount of alkali gives a measure of the 

 amount of protein digestion by trypsin.* 



Digestion of caseinogen is another method for showing the 

 digestive action of trypsin. f 



Pancreatic amylase is very similar to salivary amy'ise, 

 but is more energetic in its action. It can attack uncooked 

 starch and it produces more glucose than does the latter. 

 The production of glucose is probably due to the presence of 

 some maltase, an enzyme that hydrolyses maltose. 



Lipase hydrolyses fats with the production of glycerine and 

 fatty acids. The fatty acids combine with alkali to form 

 soluble soaps. Although the pancreatic juice is alkaline, the 

 production of fatty acids and amino acids neutralises the 

 alkali so that the intestinal contents are not sufficiently 

 alkaline to produce a pink colour with phenolphthalein. 

 Owing to the fat being insoluble the rate of hydrolysis depends 

 on the extent of surface, or in other words on the degree of 

 subdivision, hence emulsification aids the process of digestion 

 of fat. 



The manner in which bile aids the action of the pancreatic 

 enzymes can be best dealt with in connection with the digestion 

 of fat by lipase. Bile can dissolve fat, hence the concentration 

 of fat in solution is increased and the rate of hydrolysis is also 

 increased. The solvent power of bile for fat is due to the 

 presence of the bile salts. These salts have the property of 

 decreasing the surface tension at an air-water surface, and if 

 the interfacial tension at an oil-water surface be decreased the 

 emulsification of the oil will be facilitated. If the subdivision 

 of the oil proceeds far enough a true solution is produced. 

 Thus the bile salts aid the digestion of fats by increasing the 

 surface owing to emulsification and by increasing the con- 

 centration of fat in solution. The fatty acids formed by 

 hydrolysis of fats are also held in solution by the bile salts. { 



Pancreatic juice is stated to contain a milk-coagulating 

 enzyme, but this may be associated with trypsin in the same 

 way that rennin is said to be associated with pepsin. 



The action of Lipase can be shown by the amount of fatty 

 acid set free in the solution. Milk or any other fat emulsion 

 can be sterilised and rendered faintly alkaline to phenol- 

 phthalein. By the action of lipase the fats are hydrolysed and 



* S. P. L. Sorensen, Biochem. Zeit., 1908, vol. 7, p. 45. 

 f O. Gross, Arch. f. exper. Path. u. Pharm., 1908, vol. 58, p. 157. 

 J W. Marcet, Proc. Roy. Soc., 1858, vol. 9, p. 306; B. Moore and 

 D. P. Rockwood, Journ. Physiol., 1897, vol. 21, p. 58. 



