62 ENZYMES OR SOLUBLE FERMENTS. 



Trypsin. 



The proteolytic enzyme of pancreatic juice. This appears to 

 have been first separated from the other enzymes which exist 

 iTT pancreatic ]uice by DamlewskyT* More recently .Kulim 7 ""!!; i s 

 prepared it in quantity and in what must be presumed to be a 

 pure (?) form, by an elaborate and lengthy process, for the details 

 of which his original work must be consulted. 2 The composition 

 of the enzyme as prepared by Kiihne was found to be remarkably 

 complex, as shown by the fact that when dissolved in water and 

 boiled it is split up with the formation of 20 p. c. coagulated 

 proteid and 80 p. c. albumose. It might at first sight appear 

 probable from this that the purified enzyme was in reality a 

 mixture of the true enzyme with other substances (proteid) to 

 whose decomposition on boiling the coagulated proteid and albu- 

 mose were due, and some authors have taken this view. 3 This 

 seems however to be negatived by the fact that Kiihne digested 

 his trypsin for several weeks in dilute alkaline solution and did 

 not observe the formation of the least trace of peptone, leucin, 

 or tyrosin. The percentage composition of the enzyme has been 

 quoted on p. 55, from which it appears to contain distinctly less 

 carbon than a true proteid. 



Preparation of solutions of trypsin for digestion experiments.. 

 The following method due to Kiihne yields an extraordinarily 

 pure and active tryptic solution ; unfortunately it is a somewhat 

 lengthy process. 4 



One part by weight of pancreas which has been extracted with 

 alcohol and ether is digested at 40 for 4 hours with 5 parts of ! p. c. 

 salicylic acid. The residue after being squeezed out is further 

 digested for 12 hours with 5 parts of -25 p. c. Na 2 C0 3 , and the residue 

 is again squeezed out. The acid and alkaline extracts are now mixed 

 together, the whole made up to -25 '5 p. c. Na 2 C0 3 , and digested 

 for at least a week in presence of -5 p. c. thymol. By this means all 

 the first formed albiimoses are fully converted into peptones; this is 

 essential. At the end of the week the fluid is allowed to stand in 

 the cold for 24 hours, filtered, faintly acidulated with acetic acid, and 

 saturated with neutral ammonium sulphate. By this means all the 

 trypsin is separated out and may be collected on a filter, where it is 

 washed with the ammonium salt (sat. sol.) till free from peptones. 

 It is now finally dissolved off the filter in a little '25 p. c. solution 

 of Xa 2 C0 3 , to which thymol is added and thus an extremely active 

 and very pure digestive solution is obtained. Ten grams of the 

 original pancreas yield 80 100 c. c. of extract. 



1 Virchow's Arch. Bd. xxv. (1862), S. 279. 



2 VerhandL d. naturhist.-med. Ver. Heidelbg. (N.F.), Bd. I. (1876), S. 194. 



3 Low, Pfluger's Arch. Bd. xxvn. (1882), S. 209. 



* Verhand. d. naturhist.-med. Ver. Hcidelby (N.F.), Bd in. (1886), S. 463. Also 

 Ceniralb.f. d. med. Wiss. 1886, Nr. 45. 



