IT 



ACTION OF TRYPSIN ON ALBUMINS 145 



ant into peptones, peptids, and finally into amino-acids. According to 

 Gulewitsch 1 and Schwarzschild, 2 tryp.sin acts only on albumins, but 

 not on acid-amides, esters, urea-derivatives, biuret, hippuric acid, etc. 

 E. Fischer and Bergell have found, on the other hand, that some 

 dipeptids, e.g. glycyl-/-tyrosin and glycyl-^-leucin, are readily and 

 quickly dissociated by trypsin, while other dipeptids, such as glycyl- 

 glycin and leucyl-tyrosin, are apparently not acted upon. Schwarzs- 

 child 2 observed, however, that the base of Curtius (see p. 116) is 

 dissociated by trypsin. (See also footnotes on p. 125.) 



4. The Simultaneous Acid and Basic or ' Amphoteric' Character of 

 Albumins. When dealing with the salts of the albumins in Chapter 

 VI., it will be explained more fully how albumins, which in watery 

 solutions are almost neutral, have the power of combining with acids 

 and with bases to form salts. The amino-acids which build up the 

 albumin-molecule behave in every respect as do the albumins them- 

 selves, because the amino-acids retain their acid and basic character 

 owing to the fact that they become linked in such a manner that 

 the ammo-radical of one molecule unites with the tfarboxyl-radical of 

 another molecule, as has already been explained on p. 11 6. No other 

 method of linking amino-acids will preserve their double nature. 



Glycyl-glycin, 



H 2 N . CH 2 . CO NH . CH 2 . COOH, 

 and diglycyl-glycin, 



H 2 N . CH 2 . CO NH . CH 2 . CO NH . CH 2 . COOH, 



are as much amino-acids as is glycocoll itself. If the union of amino- 

 acids were brought about only through the amino-groups, the free 

 carboxyl - groups would confer on the albumin -molecule an acid 

 character, while, in the reverse case, the acid anhydrides or esters 

 would possess such marked basic properties as are possessed, e.g., by 

 the esters of the amino-acids of Curtius and E. Fischer (Cohnheim). 



The linking of radicals characteristic of albumins is therefore the 

 same as in E. Fischer's peptids, namely, the joining of amino-acids to 

 form imine-chains. It is, however, not permissible to consider albumins 



trypsin is not a single chemical substance, because he found that trypsin is very rapidly 

 destroyed by sodium carbonate, an active extract kept at 38 with 0*4 per cent Na^COg 

 having about 65 per cent of its ferment destroyed in an hour;. 1 per cent Na 2 CO ?) 

 destroys over 80 per cent, whilst pure water may destroy over 30 per cent an hour. 

 This extreme sensitiveness is, however, only obtained with the least deteriorated glycerine, 

 alcoholic, saline, and aqueous extracts of human, dog, pig, sheep, and ox pancreases, 

 while with the most deteriorated (least active) trypsin only 7 per cent of the ferment is 

 destroyed by 0'4 per cent NagCOg. 



1 W. Gulewitsch, Zeitschr. f. physiol. Chem. 27. 540 (1899). 



2 M. Schwarzschild, Hofmeister's Beitrage, 4. 155 (1903). 



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