THE INACTIVATION OF TRYPSIN. I. 



By JOHN H. NORTHROP. 



(From the Laboratories of The Rockefeller Institute for Medical Research.) 



(Received for publication, November 15, 1921.) 



In most of the early work of the kinetics of enzyme action it was 

 tacitly assumed that enzyme reactions obeyed the law of mass action 

 and that they represented a Special case of homogeneous catalysis. As 

 the individual enzymes wpre studied more carefully, however, it became 

 apparent that few, if any, obeyed the law of mass action in its simplest 

 form. Several authors have, therefore, taken the view that enzyme 

 reactions should be considered as occurring in heterogeneous systems, 

 and that owing to their colloidal nature they do not conform to the 

 law of mass action. On 'the other hand, Tammann, Michaelis, 

 Arrhenius,^ Euler,- Taylor,^' and others consider that in general the 

 law of mass action does hold and that the apparent divergencies are 

 due to secondary reactions'.'- The author has found that the peculiari- 

 ties of pepsin digestion may be accounted for in this way. It seems 

 possible to explain the kinetics of an enzyme hydrolysis fairly well 

 from either point of view. It is possible to find very close analogies 

 on the one hand with ordinary homogeneous catalysis, and on the other 

 hand with heterogeneous catalysis. From the theoretical side it 

 has been stated that since most enzymes are admittedly colloidal 

 it is not justifiable to apply the law of mass action to them. It may 

 be pointed out, however, that the work of Perrin and of Svedberg-* 

 has shown that coUpidal solutions obey the gas laws very well, in 

 fact, much better than do ionized substances. Since the law of mass 



' Arrhenius, S., Quantitative laws in biological chemistrVj London, 1915. 



' For a discussion of this question see von Eulcr, H., AUgemeine Chemie dcr 

 Enz>Tne, 2nd edition, Munich, 1900. 



^ Taylor, A. E., On fermentation, Univ. Calif. Pub., Pathology, 1903-07, 

 i, 244. 



* Svedbcrg, T., Z. physik. Chem, 1910, Lx.xiii, 547; Svcdberg, T. and Inouyc, K., 

 1911, Ixxvii, 145. Lewis, W. C. McC, A system of physical chemistry, i, 1918. 



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