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60 GENERAL AND PHYSICO-CHEMICAL.
the three above given reactions 1 and 3 can be reversed by enzymes and
indeed 1 even by using yeast (Emmerling)1
and 3 with emulsin (Rosen-
thaler 2
) . In the last instance the reaction is asymmetric in that
the d-form of the mandelic acid nitrile is formed. The asymmetric C
atom is marked in the above formula. Subsequently Rosenthaler was
able to divide the emulsin into a splitting component (5-emulsin) and
a synthetical form (or-emulsin)3
. In connection with the views on the
structure and mode of action of enzymes it is of special interest that
recently Bredig and Fiske 4
have been able to prepare the two optical
antipodes of mandelic acid nitrile from benzaldehyde and hydrocyanic
acid by means of optically active catalysts. By using quinine as
catalyst the dextro-rotatory nitrile was formed and by quinidine (iso-
meric with quinine but opposed in regard to rotation power) the laevo-
rotatory nitrile was formed. This indicates that possibly the enzymes
also have an asymmetric structure. The synthetic formation of gluco-
sides by the aid of emulsin has also been performed by van’t Hoff.5
An undoubted synthesis of fat and other ester-like combinations
of fatty acids is also known. Kastle and Loevenhart 6
have shown
the formation of ethyl butyrate from ethyl alcohol and butyric acid
under the influence of a pancreas enzyme. In an analogous manner
Hanriot 7
obtained monobutyrin from butyric acid and glycerin with
blood serum. Pottevin 8
by means of a pancreas enzyme transformed
oleic acid and glycerin into mono- and triolein as well as oleic acid esters
with monatomic alcohols. The synthetical action of the pancreas has
been closely studied bjr
Dietz.9
The enzyme used by Dietz was insoluble in water, and its action was tested
with z’-amyl alcohol and n-butyric acid or the corresponding ester. It was shown
that the reaction took place in the insoluble phase (enzyme). From the formula
alcohol -f acid tester +water, it follows that when the molecular concentrations
of alcohol, aeid, ester and water are designated Ca, Cs. Ce. Cw, the reaction velocity
dx
of the ester formation for a homogeneous system is -j7=k1 .CA-Cs—ki.CE.Cw (see
dx
page 32), which equation can be simplified to -rr = ki.Cs—k2 .CE as the alcohol
and water were in excess and their concentration considered as constant and
included in the constants h and k2 . At equilibrium we have kiCs=k2Cs or
1
Ber. d. d. chem. Gesellsch., 34, 3810 (1901).
* Bioch. Zeitschr., 14, 238 (1908).
»
Ibid., 17, 257 (1909).
Bioch. Zeitchr, 46, 7 (1912).
8
Sitzungsber. preuss. Akad. Wiss., 1909, s. 1065; 1910 s. 963.
8
Arner. Chem. Journ., 24, 491 (1900).
7
Compt. rend., 132, 212 (1901).
»nnd., 136, 1152 (1903), 138, 378 (1903); Ann. Inst. Past., 20, 901 (1906).
• Zeitschr. f. physiol., Chem., 52, 279 (1907).
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