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 (o--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 G 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 by DiETZ. 9 



The enzyme used by DIETZ was insoluble in water, and its action was tested 

 with t-amyl alcohol and w-butyric acid or the corresponding ester. It was shown 

 that the reaction took place in the insoluble phase (enzyme). From the formula 

 alcohol +acid<=ester -f- water, it follows that when the molecular concentrations 

 of alcohol, acid, ester and water are designated CA, Cs, CE, Cw, the reaction velocity 



of the ester formation for a homogeneous system is -T^ki.CA.Cskz.CE.Cw (see 



dx 

 page 32), which equation can be simplified to -^ =ki.Cs kz.Cs as the alcohol 



and water were in excess and their concentration considered as constant and 

 included in the constants ki and & 2 . At equilibrium we have kiCs=k 2 Cs or 



1 Ber. d. d. chem. Gesellsch., 34, 3810 (1901). 



2 Bioch. Zeitschr., 14, 238 (1908). 

 8 Ibid., 17,257 (1909). 



4 Bioch. Zeitchr., 46, 7 (1912). 



6 Sitzungsber. preuss. Akad. Wiss., 1909, s. 1065; 1910 s. 963. 



Amer. Chem. Journ., 24, 491 (1900). 



7 Compt. rend., 132, 212 (1901). 



/We*., 136, 1152 (1903), 138, 378 (1903); Ann. Inst. Past., 20, 901 (1906). 



Zeitschr. f. physiol., Chem., 52, 279 (1907). 



