TRYPSIN AND TRYPSIN DIGESTION. 481 



can be obtained after a few days by allowing the finely divided gland 

 to stand with water which contains 5-10 cc. chloroform per liter ($AL- 

 KOWSKI) at the temperature of the room. This infusion can be kept 

 very active for several years at the cellar temperature. For digestion 

 experiments the active commercial trypsin preparations can be employed. 



Like other enzymes, trypsin is characterized by its action, and this 

 action consists in dissolving protein and in splitting it into simpler prod- 

 ucts, mono- and diamino-acids, tryptophane, etc., in alkaline, neutral, 

 and indeed in very faintly acid solutions. This action has been so far 

 considered as characteristic for trypsin. Recent investigations seem to 

 indicate that this action is not due to one enzyme alone, but to the com- 

 bined action of several enzymes. 



Although contrary to MAY'S statement, there is no question that 

 there occurs in the pancreas besides trypsin an enzyme similar to erepsin 

 (BAYLISS and STARLING, VERNON l ). According to the latter this erepsin 

 has a strong action upon peptone, and he believes that the peptone- 

 splitting action of a pancreas infusion is in great part due to the erepsin. 

 The pancreas besides these also contains a nudease (see page 469), whose 

 relation to pancreas erepsin has not been determined. 



The unity of trypsin has also been disputed from another point of view. 

 According to POLLAK the trypsin (in the ordinary sense) contains a second 

 enzyme, which does not act upon protein, but- only upon gelatin, and he calls 

 this enzyme glutinase. This glutinase is much more resistant toward acids 

 than trypsin, and by proper treatment with acids POLLAK was able to change a 

 pancreas infusion so that it acted upon gelatin and not upon certain proteins. 

 The correctness of these observations has, indeed, not been generally accepted, 

 and it is disputed by ASCOLI and NEPPi. 2 According to them the action of the 

 trypsin is weakened by the acid, and indeed to such varying degrees for differ- 

 ent proteins that the action upon albumin is lost while the action upon gelatin 

 is noticeable. Nevertheless, we here have a warning to be careful as to the 

 conclusions drawn from results where impure infusions are used. For many 

 experiments it is undoubtedly advisable to use the natural pancreatic juice. 



The following reports on the action of trypsin applies to the so-called 

 trypsin, with the reservation that it is perhaps not a unit enzyme. 



The action of trypsin on proteins is best demonstrated by the use of 

 fibrin. Very considerable quantities of this protein body are dissolved 

 by a small amount of trypsin at 37-40 C. It is always necessary to 

 make a control test with fibrin alone, with or without the addition of alkali. 

 Fibrin is dissolved by trypsin without any putrefaction; the liquid has 

 a pleasant odor somewhat like bouillon. To completely exclude putre- 

 faction a little thymol, chloroform, or toluene should be added to the 



1 Bayliss and Straling, Journ. of Physiol., 30; Vernon, ibid., 30; and Zeitschr. f. 

 physiol. Chem., 50; Mays, ibid., 49 and 51. 



2 Pollak, Hofmeister's Beitrage, 6; contradictory statements are found in Ehren- 

 reich, cited in Bioch. Centralbl., 4; Ascoli and Neppi, Zeitschr. f. physiol. Chem., 56. 



