ENZYMES. 55 



live influences (heat, alkalies) 1 ; According to this only that part of the 

 added enzyme which is combined with the substrate is active. In 

 judging of the rapidity of enzyme reactions the following must be con- 

 sidered: 



1. The velocity with which the enzyme combines with the substrate. 



2. The result of the division, i.e., how much of the added enzyme 

 is combined with the substrate. 



3. The velocity of the chemical processes produced by the enzyme. 



The velocity of the combination of the enzyme with the substrate (1) can at 

 least in many cases be ignored in consideration of the time necessary for the 

 chemical reaction (see page 37). This applies to those cases where the chemical 

 transformation in the presence of an excess of substrate at the beginning of the 

 processes remains the same in each successive time interval. The quantity of 

 enzyme combined with the substrate, does not, in these cases, increase with the 

 time, which would be the case if the time necessary for the combination is not in 

 comparison with that for the chemical reaction. Equal decomposition for equal 

 time at the beginning of the processes have been found for the following enzymes 

 invertase, 2 diastase, 3 trypsin with casein, 4 as substrate. 



The second question, as to the division of the enzyme between different phases 

 we will discuss after we have spoken of the velocity of the real chemical reaction 

 (page 58) as well as the retardation of enzyme action (page 62). 



In regard to the chemical reaction they proceed probably in a different 

 manner according to the kind of combination between the substrate and 

 the enzyme. In one case we can consider that the combination of the 

 enzyme with the substrate is of such a kind that both form a homogeneous 

 phase and that one serves as solvent for the other (page 27). In this 

 case the chemical reaction produced by the enzyme takes place in a 

 homogeneous medium. Secondly, we can consider the combination of 

 the substrate and enzyme as an adsorption combination (see page 27) 

 in which case the combination does not form a homogeneous phase and 

 the reaction differs more or less from one taking place in a homogeneous 

 system. Bearing this in mind it would be interesting to investigate 

 whether the facts found for enzymotic reactions correspond with 

 catalytic reactions in homogeneous media. 



For these latter the following laws (see page 33) have been found: 



1. When the quantity of catalyst remains constant, the reaction 



1 O'Sullivan and Thompson, Journ. Chem. Soc., 57, 926 (1890); Bayliss and Starling, 

 Journ. of PhysioL, 30, 71 (1903); Hedin, ibid., 30, 173 (1903); 32, 474 (1905); Taylor, 

 Journ. of biol. Chem., 2, 90 (1906). 



2 O'Sullivan and Thompson, Journ. Chem. Soc., 57, 926 (1890); Ducleau, Traite 

 de microbiologie II, 137; Brown, Trans. Chem. Soc., 81, 373 (1902); Armstrong, 

 Proc. Roy. Soc., 73, 500 (1904); Hudson, Journ. Amer. Chem. Soc., 30, 1160, 1564 

 (1908). 



3 Brown and Gliddinning, Proc. Chem. Soc., 18, 43 (1902). 

 * Hedin, Journ. of Physiol., 32, 471 (1905). 



