GENERM. i'if<)i'i:irrii:s or i:\/.y\ii:h 59 



or by removal from the cell or entrance into it of materials which over- 

 halance one side of the equation. 



In just Avhat manner the enzymes accomplish tlicir catalytic effect 

 is yet unknown.^- A favorite idea is that they form loose compounds 

 Avith the substance to be split and with water ; the resulting compound 

 being unstable and breaking down, the water remains attached to 

 the components of the substance. 



Enzymes do not act eatalytically on all substances by any means, 

 but show a decidedly specific nature. The}' affect only organic sub- 

 stances, and the actions are limited to two processes — hydrolysis and 

 oxidation, or the reverse processes of dehydration and reduction.^^ 

 The most essential difference between the enzymes and the chemicals 

 that can accomplish hydrolysis or oxidation is this : the ordinary 

 -chemical reagents produce their effects on many sorts of substances, 

 whereas the enzymes are specific ; thus hydrochloric acid will hydrolyze 

 starch or protein with equal facility, but pepsin will not affect starch 

 at all. 



The very specific nature of the enzymes, their activation by other 

 l^ody products, the fact that they seem to be bound to the substance 

 upon which they act, that they are susceptible to heat, and that they 

 produce immune bodies when injected into experimental animals, all 

 suggest the probability of a relationship hettveen enzymes and toxins. 

 This matter will be discussed more fully in considering the chemistry 

 of immunity against enzymes. 



General Properties of Enzymes. — Other properties of enzymes 

 may be briefly mentioned. The speed of reaction they produce in- 

 creases with the amount of enzymes present, but not in direct propor- 

 tion (except with rennin). Very dilute acids favor the action of 

 nearly all fennents, and alkalies are unfavorable for all but trypsin, 

 ptyalin, and a few others. Weak salt solutions also are more favor- 

 able than distilled water. (These facts suggest strongly the possi- 

 l)ility that ions play an important role in the process.) Water and 

 dilute glycerol dissolve enzymes, which form always colloidal solutions 

 that are very slightly dialyzable ; and they may be precipitated from 

 solution by alcohol, and redissolved again with but slight impairment 

 of strength. Filtration through porcelain filters is not complete, from 

 10 to 25 per cent, of most enzymes being lost in each filtration and 

 enzj'mes are subject to great absorption by surfaces, e. g., charcoal, 

 kaolin." As before mentioned, many chemicals poisonous to bacteria 

 have little influence on most enzymes, but nearly all substances when 

 concentrated are injurious or destructive, and some enzymes are 



12 See Euler, "Chemical Dynamics of Enzyme Reactions." Ergebnisse d. Pliysiol., 

 1910 (9), 241. * " . _ 



13 Alcoholic fermentation may be an exception, the change being C„II,;Oc — 

 2CoH,, -f 2C0.,, but it is very possibly an intramolecular oxidation. 



14 See Hedin, Ergebnisse d. Phvsiol'., 1910 (9), 433. 



