ENZYMES. 57 



The second law for catalytic reactions which we have formulated, 

 that with constant quantities of substrate the reaction velocity is pro- 

 portional to the quantity of enzyme, has been shown in certain cases 

 where the substrate was in excess (practically constant quantity) namely 

 with kephir lactase, 1 trypsin with casein as substrate. 2 In the just- 

 mentioned monomolecular enzyme reactions the velocity coefficient in 

 a few cases was found proportional to the quantity of enzyme (catalase 

 from blood, 3 erepsin with glycyl-glycine as substrate, 4 pancreatic lipase 5 ) 

 and in others not (catalase from Boletus scaber, lipase from pig fat). 6 

 It has been shown for several enzymotic reactions that with the same 

 substrate the same decomposition can be obtained if the time of action 

 varies in inverse proportion to the added quantity of enzyme. If p is 

 the quantity of enzyme and t the time of action, then the decomposition 

 is the same in all tests where p.t is the same figure. This rule has been 

 found true for the following enzymes: saccharase (O'SuLLiVAN and 

 THOMPSON as well as HUDSON 7 ), pepsin (SjOQViST 8 ), rennin (especially 

 FuLD 9 ), peptone-splitting enzyme (VERNON 10 ), fibrin ferment of snake 

 poison (MARTIN n ), trypsin (HEDIN 12 ), pepsin, rennin, trypsin, pyocy- 

 aneus protease (MADSEN 13 ). On the action of trypsin upon casein this 

 law has been shown correct for different stages in the reaction. 14 This 

 indicates that the progress of the entire reaction remains the same with 

 different quantities of enzyme, only that the time for the same decom- 

 position is inversely as the quantity of enzyme. As clearly shown by 

 HEDIN, this indicates that the velocity coefficient is proportional to the 

 quantity of enzyme which is called for by the second law. If we start 

 with the above-mentioned assumption that only that enzyme is active 

 which is combined, then it follows from the proportionality between the 

 velocity coefficient and the quantity of enzyme, that always the same 

 fraction of the enzyme is combined with the substrate, or that the divi- 

 sion of the enzyme remains independent of the quantity. 



Armstrong, Proc. Roy. Soc., 73, 500 (1904). 



2 Hedin, Journ. of PhysioL, 32, 471 (1905). 



3 Senter, Zeitschr. f . physik. Chem., 44, 257 (1903). 

 4 Euler, Zeitschr. f. physiol. Chem., 51, 213 (1907). 



5 Kastle and Loevenhart, Amer. Chem. Journ., 24, 491 (1900). 

 6 Euler, Hofmeister's Beitrage, 7, 1 (1906). 



7 Trans. Chem. Soc., 57, 926, 1890; Journ. Amer. Chem. Soc., 30, 1160, 1564 (1908). 



8 Skand. Arch. f. Physiol., 5, 358 (1895). 



9 Hofmesietr's Beitrage, 2, 169 (1902). 



10 Journ. of Physiol., 30, 334 (1903). 



11 Ibid., 32, 207 (1905). 



12 Ibid., 32, 468 (1905); 34, 370 (1906). 



13 Arrhenius, Immunochemie, Leipzig, 1907, 46. 

 "Zeitschr. f. physio!. Chem., 57, 478 (1908). 



