VITAL PHENOMENA 81 



cyanhydrin is formed. E. Fischer (1898) observed that beta- 

 methyl-d-glucoside is split by emulsin whereas alphamethyl-d- 

 glucoside is not. 



This form of specificity is not peculiar to enzymes. According 

 to Bredig and Fajans (1908) the splitting of camphocarbonic 

 acid into camphor and C0 2 is accelerated by certain organic com- 

 pounds. Natural nicotine decomposes d-camphocarbonic acid 

 12 per" cent faster than 1-isomere. Chinin decomposed the 

 1-isomere 46 per cent faster than the d-isomere. 



The specificity just mentioned is quantitative and not qualita- 

 tive, whereas the specificity of enzymes is supposed to be qualita- 

 tive. It was shown by H. D. Dakin (1905), however, that the 

 specificity of lipase for certain d-esters in preference to the 

 isomeric 1-esters, is quantitative. 



More unexpected than the specificity of enzymes, is the change 

 in specificity on reversing the reaction. A. Croft Hill (1898) 

 succeeded in synthesizing a disaccharide from dextrose by means 

 of maltase from yeast. Emmerling (1901) showed that this di- 

 saccharide is not maltose, as was to be expected, but isomaltose. 

 E. F. Armstrong (1903) continued this investigation and found 

 that: 



whereas maltose is split into glucose by maltase 

 glucose is synthesized to maltose by emulsin, and 

 whereas isomaltose is split into glucose by emulsin 

 glucose is synthesized to isomaltose by maltase. 



The explanation of this anomaly is that the enzymes change 

 the point of equilibrium of these reversible reactions. In a mix- 

 ture of maltose and glucose, maltase displaces the equilibrium 

 toward the side of the glucose, whereas emulsin displaces it 

 toward the side of the maltose. If HC1 is used as a catalyzer, 

 when equilibrium is established glucose, maltose and isomaltose 

 are present in the same proportions, irrespective of the first used. 

 If glucose only is present at the start, and maltase is used, very 

 much more isomaltose than maltose is formed, but if emulsin is 

 used, much more maltose than isomaltose. 



Since enzymes merely accelerate reactions that would take 

 place without them and all reactions are theoretically reversible, 

 the synthesis of complex bodies from their decomposition pro- 



