54 ENZYMES 



susceptibility to poisons of enzymes and cells.^ Strengths of certain 

 antiseptics that will either destroj^ or inhibit the action of living cells, 

 such as alcohol, ether, salicylic acid, thymol, chloroform, toluene and 

 sodium fluoride, will harm free enzymes in solution little or not at all. 

 This fact has been of great assistance in distinguishing between the 

 action of enzymes and of possible contaminating bacteria in experi- 

 mental work. Although this difference between enzymes and cells is 

 characteristic, it does not finally decide that tlie cell actions are not 

 enzyme actions, for it may well be that the poisons act chiefly by 

 altering the physical conditions of the cell so that diffusion is inter- 

 fered with, thus seriously interfering with the exchange of cleavage 

 products between different parts of the cell, and cheeking intracellu- 

 lar enzyme action, which we shall see later requires free diffusion of 

 the products for its continuance. At the very least, however, we may 

 look upon the intracellular enzymes as the most important known 

 agents of cell metabolism, and consequently of all life manifestations, 

 and the changes they undergo or produce in pathological conditions 

 must be fully as fundamentally important as is their relation to 

 physiological processes. It therefore becomes necessary for us to 

 consider carefully — 



THE NATURE OF ENZYMES AND THEIR ACTIONS - 



Since up to the present time no ferment has been isolated in an 

 absolutely pure condition we are entirely unfamiliar with their chemi- 

 cal characters, and consequently are obliged to recognize them solely 

 by their action. As far as we know, true enzymes never occur except 

 as the result of cell life — they are produced within the cell, and in- 

 creased in aniount by each new cell that is formed, and, furthermore, 

 they are present in every living cell without exception. As the same 

 facts are equally true of the proteins, and apjiarently true of nothing 

 else, it is natural to associate the enzymes with proteins, and so ex- 

 plain the importance of the proteins for cell life.^ If enzymes are 

 obtained in any of the usual ways from animal cells or secretions 

 they are always found to give the reactions for proteins, even if re- 

 purified many times. But it is well known that whenever proteins 

 are precipitated the other substances in the solution tend to bo dragged 



1 See discussion by Vernon, Er<?Gbniase d. Pliysiol., 1910 (0), 2.34. 



2 It would not bo profitable to discuss fnllv all the various tlioorics and hy- 

 potheses that have been advanced, but the reader is referred to the followinir chief 

 compilations of tlie entire subject: Oppcnlieinier, '"Die F(M-nienlc uiid ihre \Mrk- 

 unpen," Leipzip; P>ayliss, "The Nature of l^'n/.ynie AcUon." I\l(Uioij;ra|)lis on Bio- 

 chemistry, London: Stern, "Pliysico-cliemical Pasis of I'erinent Action," in Oppen- 

 heimer's "Ilandbuch d. P.iochemie," Vol. 4, pt. 2: Samuelcy, "Animal Ferments." 

 ibid. Vol. I; A. E. Taylor, "On Fermentation," T^niv. of California Publications; 

 Euler, "General Chemistrv of tlie Enzvmes," translated bv T. IT. Pope, New York, 

 1912. 



3 Another impfirtaiit point is that the closest imitation of cn/yin(>s, Bredig's 

 "inorganic ferments," seem to owe their action to th(>ir colloidal nature. 



