20 STUDIES IN PLANT RESPIRATION AND PHOTOSYNTHESIS. 



results have recently been obtained which are pertinent to the 

 general subject of the role of amino-acids in respiration. 



Various claims have been advanced from time to time regarding 

 the artificial production of enzymes, and a number of catalytic 

 reactions have been produced by means of these products — reactions 

 which are very closely analogous to those produced by enzymes. 

 In the extensive literature on this subject a very serious error has 

 been allowed to enter — a matter of inference originally rather than 

 of direct statement. It is a very debatable question whether the 

 results with these "artificial enzymes," i. e., mixtures of substances 

 which induce certain reactions, which are also produced by true 

 enzymes, are of such great value in revealing the composition of the 

 enzymes as has been claimed. It appears rather that these reactions 

 can be induced by a variety of catalyses, as has been found to be 

 the case for many inorganic and organic reactions, and simply that 

 it has been possible for chemists to produce one of these catalysts. 

 However, it does not now follow that this is necessarily the same 

 catalyst which is produced and used by the organism in the form of 

 an enzyme. The point is essentially one of interpretation of experi- 

 mental results. 



Nevertheless, the results obtained with these various "artificial 

 enzymes" are of great value in explaining catalytic action, and 

 therefore are of direct bearing on enzyme activity. Herzfeld* has 

 shown that the action of the proteolytic enzymes, pepsin and 

 trypsin, can be simulated by a prepared mixture of amino-acids and 

 polypeptides. According to this author's views, autolysis is simply 

 an autocatalysis which is started by the introduction into the system 

 of some of the products of decomposition. Baur and Herzfeld^ 

 have carried these researches further, and announce a splitting of 

 glucose into alcohol and carbon dioxid by means of carefully prepared 

 mixtures containing peptone, bile salts, dextrin, and sodium bicar- 

 bonate. Although the proportion of carbon dioxid and alcohol 

 formed in these reactions does not correspond to that obtained in 

 zymase fermentation, the authors explain this by the fact that their 

 catalyst also produces other sugar decompositions. Provided the 

 toluene employed to prevent infection by living organism was 

 thoroughly efficacious, which is open to some doubt, these experiments 

 point the way to a very fruitful field in the investigation of enzyme 

 activity. 



>Herzfeld, E., Biochem. ZeUschr., 64, 103-105 (1914); 68, 402-435 (1915); 88, 260 (1918). 

 * Baur, E.. and E. Herzfeld. Biochem. Zeitschr., 117, 96-112 (1921). 



