Full resolution (JPEG) - On this page / på denna sida - VIII. Digestion - IV. The Pancreas and Pancreatic Juice
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
ACTION OF TRYPSIN. 505
this enzyme glutinase. This glutinasc 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.1
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 putrefaction a little thymol, chloroform, or toluene should be
added to the liquid. Tryptic digestion differs essentially from peptic
digestion, irrespective of the difference in the digestive products, in that
the first takes place in neutral or alkaline reaction and not, as is neces-
sary for peptic digestion, in an acidity of 1-2 p. m. HC1, and further
by the fact that the proteins dissolve in trypsin digestion without pre-
viously swelling up.
As trypsin not only dissolves proteids, but also other protein sul -
stances such as gelatin, this latter body may be used in detecting tryp-
sin. The liquefaction of strongly disinfected’ gelatin is, according to
Fermi, 2
a very delicate test for trypsin or tryptic enzymes. Various
suggestions for the use of gelatin in the trypsin test have been made.
In consideration of the observations of Ascoli and Neppi that a trypsin
may not act upon fibrin or other proteids but still digest gelatin, it is
advisable never to make use of gelatin or proteid alone in testing for
trypsin, but always the two.
For the quantitative estimation of trypsin by measuring the rapidity of
digestion we generally make use of the method of Mett, described under pepsin
digestion. Another method, suggested by Weiss, consists in determining the
nitrogen in the filtrate after coagulation with heat and acetic acid. Lohlein
recommends the titration method of Volhard as used in pepsin determinations,
and has given directions for its use. Jacoby recommends the use of (ricin, and
Gross suggests a method based upon the precipitation of casein by acid. Bay-
1
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.
2
Arch. f. Hyg. 12 and 55.
<< prev. page << föreg. sida << >> nästa sida >> next page >>
