PANCREATIC DIGESTION. H 1 



globulin, proteose and peptone; nucleoprotein is also present in traces. 1 

 The average daily secretion of pancreatic juice is 650 c.c. and its 

 specific gravity is 1.008. The fluid contains 1.3 per cent of solid 

 matter and the freezing-point is 0.47 C. The normal pancreatic 

 secretion contains at least four distinct enzymes. They are trypsin, 

 a proteolytic enzyme; pancreatic amylase (amylopsin), an amylolytic 

 enzyme; pancreatic lip&se (steapsin), a fat-splitting enzyme: and 

 pancreatic rennin, a milk-coagulating enzyme. Lactase, the lactose- 

 splitting enzyme, is also present at certain times. 



The most important of the four enzymes of the pancreatic juice is 

 the proteolytic enzyme trypsin. This enzyme resembles pepsin in so 

 far as each has the power of breaking down protein material, but 

 the trypsin has much greater digestive power and is able to cause a 

 more complete decomposition of the complex protein molecule. In 

 the process of normal digestion the protein constituents of the diet 

 are for the most part transformed into proteoses (albumoses) and 

 peptones before coming in contact with the enzyme trypsin. This is 

 not absolutely essential however, since trypsin possesses digestive ac- 

 tivity sufficient to transform unaltered native proteins and to produce 

 from their complex molecules comparatively simple fragments. 

 Among the products of tryptic digestion are proteoses, peptones, 

 peptides, leucine, tyrosine, aspartic acid, glutamic acid, alanine, phen- 

 ylalanine, glycocoll, cystine, serine, valine, proline, oxy proline, iso- 

 lencine, arginine, lysine, histidine and tryptophane. (The crystalline 

 forms of many of these products are reproduced in Chapter IV.) 

 Trypsin does not occur preformed in the gland, but exists there 

 as a zymogen called trypsinogen which bears the same relation to 

 trypsin that pepsinogen does to pepsin. Trypsin has never been 

 obtained in a pure form and therefore very little can be stated 

 definitely as to its nature. The enzyme is the most active in alkaline 

 solution but is also active in neutral or slightly acid solutions. 

 Trypsin is destroyed by mineral acids and may also be destroyed by 

 comparatively weak alkali (2 per cent sodium carbonate) if left in 

 contact for a sufficiently long time. Trypsinogen, on the other 

 hand, is more resistant to the action of alkalis. In pancreatic di- 

 gestion the protein does not 'swell as is the case in gastric digestion, 

 but becomes more or less " honeycombed " and finally disintegrates. 



The pancreatic juice which is collected by means of a fistula 

 possesses practically no power to digest protein matter. A body 

 called enter okinase occurs in the intestinal juice and has the power 



1 Glaessner : Zeitschrift fur physiohgische Chemie, 1904, 40, p. 476. 



