TIIK KN/YMKS AM) M. TKArHI'/S TIIKORY 17 



18. The Enzymes and M. Traube's Ferment Theory. 



There is still another possible explanation of the power of living cells to act, 

 at a distance. This regards the cells, not as centres of radiating molfcnl.ii 

 movements, but as forming centres of production of metabolic products which 

 penetrate through the cell membrane into the surrounding liquid. There they 

 become widely distributed by diffusion, and by their influence bring about tin; 

 decomposition of certain constituents of the solution, but do not undergo ;my 

 chemical change themselves. These active bodies are called enzymes, :md their 

 behaviour is, as will be observed, different from that of ordinary dminiml agents, 

 since the latter effect alterations in other groups of atoms by their chemical 

 affinity, whereby the old combination is broken up, and the separated portion 

 enters into a new atomic grouping with a part of the active agent. Accordingly, 

 a definite weight of the agent can only displace a definite quantity (known as the 

 "equivalent weight") of other compounds ; whereas the enzymes behave differently, 

 their activity being practically illimitable. They do not combine with the pro- 

 ducts of the reaction, but continue to act on the residual undecomposed substance. 



The first enzyme was discovered by PAYEN and PERSOZ (I.) in 1833, who 

 detected in malt extract a substance which they termed diastase capable of 

 converting starch into sugar. They were, however, unable to isolate it in a pure 

 condition. Three years later THEODOR SCHWANN (III.) discovered in gastric 

 juice pepsin, subsequently also named peptase, which in faintly acid solutions 

 resolved undiffusible albumen into assimilable dissociation products. Since that 

 time the same enzyme has also been detected in various vegetable organisms, 

 many varieties of bacteria in particular having the power of elaborating it. 

 There will be ample opportunity for reference to this point along with the other 

 known enzymes at a subsequent stage. At present we have only to consider them 

 as the basis of a theory of fermentation, the formulation of which dates back as 

 far as 1858, but has come to the front more of late years, and so far as can be 

 judged from the data at present available will acquire still greater importance. 



As we have observed in 10, the meaning attached, under the influence of 

 alchemical views, to the word ferment was, until the close of the eighteenth 

 century, very comprehensive, and it was only then that the restriction of the 

 term to bodies inciting fermentation began. Contemporaneous with the develop- 

 ment of positive knowledge with regard to these bodies was the discovery of the 

 enzymes, the behaviour of which resembled that of the former, in so far that 

 they exhibited a capacity of inducing decomposition. Moreover, the obscurity 

 in which these organisms were still enshrouded was equally mysterious in both 

 cases ; and, since the organic nature of the true instigators of fermentation was 

 either unknown or was not considered worth attention by the chemists of the day, 

 it happened that the name " ferment " was also applied to the newly discovered 

 enzymes. With an increasing insight into the true state of the matter grew the 

 conviction that two very different things had been grouped under one name, and 

 this conviction found expression in the distinction thenceforward of the true 

 instigators of fermentation as organised or structural ferments, whilst the enzymes 

 were designated unorganised or structureless ferments. These terms are still 

 current ir- chemical text-books, whereas in Fermentation Physiology it is customary 

 to speak merely of fermentative organisms on the one hand and of enzymes on 

 the other. 



M. TRAUBE(!. and II.) in 1858 made the origin and influence of these enzymes 

 the basis of a new conception (Ferment Theory) of fermentation, according to 

 which this process is not instigated by the organisms themselves, but by the 

 enzymes formed as products of their vitality and excreted by them. 



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