Page 10 - ALLEN'S COMMERCIAL ORGANIC ANALYSIS A TREATISE ON THE PROPERTIES, MODES OF ASSAYING... VOL VIII

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4
6 ENZYMES. ,

extracts is now being studied by a commission appointed by the
Society of Dyers and Colourists. (See Appendix.) \

SUCROCLASTS.

Invertase is obtained by extracting fresh yeast with chloroform
water, air-dried yeast with water or by filtering yeast which has been
allowed to autolyse, By precipitating with alcohol it is obtained free
from maltase and most other enzymes.'
Maltase is only obtained by extracting air-dried yeast with water.
It is destroyed on precipitation with alcohol.
Emulsin is best obtained from sweet almonds. The oil is expressed
and the press cake extracted with water at about 1o-2o. Protein is
removed from the extract by means of a little acetic acid (a drops per
too c.c. of liquid); to the filtrate an equal volume of alcohol is gradually
added and a granular precipitate of enzyme obtained. This is washed
with alcohol and immediately redissolved in water; a colourless
clear liquid is so obtained admirably suited for polarimetric work.
(See Armstrong, Proc. Roy. Soc., 1908, Series B, 80, 324.)
Lactase is obtained in a similar manner from some but not all
preparations of kephir.

Qualitative.
Invertase. The enzyme solution is incubated with 1o sucrose
for half an hour at 37° and the reducing power tested with Fehling's
solution. With active preparations the hydrolysis is very rapid.
Emulsin. The enzyme solution is incubated for a few hours
with 2% salicin. Hydrolysis is shown by the solution reducing Feh-
ling's solution and giving a purple colouration with ferric chloride.
Alternatively amygdalin may be used as test material and the for-
mation of hydrogen cyanide identified with picric paper (filter
paper soaked in a solution of 10 grm. sodium carbonate and t grm.
picric acid per rooc.c.) which becomes a deep brick red. This test is
especially suitable when the enzyme is to be identified in plant or
animal extracts containing reducing and colouring substances which
obscure the test with salicin.
a
L
Lactase, Maltase. ctose and maltose are used as test ma-
terials; 5% solutions are incubated some hours at 37°. Change is
demonstrated by the use of Barfoed's reagent (Vol. 1, page 333) which is
reduced by dextrose and not by the disaccharides. A more certain
Compare Vol, 1, pa8e 314, also O'Sullivan and Tompson,J. Chem. Soc,, [1890]. 57, 834.