ARTICLES 413 



support the specificity of enzymes, there are many facts which 

 as at present understood throw doubt on absolute specificity. 

 Some consider that the work of Armstrong and Horton (191 3) 

 negatives specificity, as they found that a series of varied effects 

 could be obtained from the action of emulsin on different 

 glucosides. Similarly Fajans (19 10) had shown that emulsin 

 acts on a- and /3-glucosides, but more rapidly on the /3-glucoside, 

 whereas maltase has the opposite effect. Some, on the other 

 hand, show that enzymes may take part in reactions which 

 could not occur in nature, and hold that there are cases of 

 extremely rapid adaptation — which is unlikely — or of non- 

 specificity of the enzymes concerned. For example, Kondo 

 (19 1 2) found that the liver could synthetise amino-acids from 

 the keto-acids and ammonia, even if the keto-acids used were 

 not those which occur in the body proteins. Working on fungi, 

 Pringsheim (19 10) found that they could act on both isomers 

 of amino-acids, but at different rates ; while similar work was 

 done by Dox and Neidig (191 2) with reference to the action of 

 aspergillus on glucosides. Explanation, however, may be 

 offered for these apparent anomalies. Thus some workers 

 hold that emulsin is composed of several enzymes, and — as 

 Bayliss suggests — it is possible that under certain circum- 

 stances enzymes may change the condition of an optically active 

 body, as may be done by inorganic catalysts. The hypothesis 

 put forward by the Armstrongs (191 3) must here be noted. 

 Reference will be made to it later, but for our present need 

 it may be put briefly thus. It is supposed that the enzyme 

 has a double function and is composed of two parts, viz. the 

 acceptor, which is responsible for the adsorption, and the agent, 

 which carries out the chemical change. The Armstrongs hold 

 that the specificity of enzymes depends on the fact that the 

 acceptor portion is closely allied to, if not identical with, a 

 dominant group in the hydrolyte. Unfortunately it has not 

 yet been possible to demonstrate what groups in the molecules 

 concerned are responsible for the combination. Of interest too 

 is the electron theory of Gallerani (19 14), who put forward the 

 suggestion that enzymes act somewhat like radioactive sub- 

 stances. He considered that the specificity of an enzyme 

 action was connected with a peculiar syntony and synchronism 

 which exists between the electrotonic intra-atomic motion of 

 the agent and that of the element acted upon. Meantime, 

 therefore, it may be considered that enzymes are specific 

 towards certain groups of substances, but in the light of our 

 limited knowledge of the exact nature of enzymes themselves, 

 the trend of increasing evidence is towards absolute specificity. 

 Velocity. — As has already been said, enzymes are catalysts 

 and, as such, manifest their existence by changing the rates at 



