64 PHYSICAL CHEMISTRY IN BIOLOGY. 



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 assumptioa 

 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 division of the enzyme remains independent 

 of the quantity. In regard to the division of the enzymes REICHEL 

 and SPIRO 2 claim that rennin also during and after coagulation is divided 

 according to a constant factor between the whey and curd. 



In determining the quantity of enzyme the so-called SCHUTZ'S rule plays 

 an important part. In its newest form this is, that the decomposition is pro- 

 portional to the square root of the quantity of enzyme and the time, or decom- 

 position = k *^pt where k is a constant, p the quantity of enzyme and t the 

 time of the action. This was first jshowri by SCHUTZ 3 for pepsin and indeed, 

 in this form, decomposition = k^p as the time (t) was constant. The form 

 decomposition = k\^pt was given by SCHUTZ, and HuPFERT. 4 According to 

 PAWLOW this rule also applies to trypsin digestion. 5 SCHUTZ'S rule, is good for 

 a certain stage of digestion only and it indicates that the extent of the validity 

 must be very dependent upon the method used for the determination of the 

 decomposition as the different digestion products are determined by different 

 methods. It must also be remarked that within the entire domain where 

 SCHUTZ'S rule is applicable the same value for pt must correspond to the same 

 decomposition, and necessarily the above-discussed enzyme-time rule must also 

 be valid. SCHUTZ'S rule has also been proven for the action of gastric and pan- 

 creatic lipase. 6 According to ARRHENIUS 7 the validity of the rule can be explained 

 by the assumption that the enzyme combines with the reaction products so that 

 the active mass of enzyme changes in inverse proportion to the quantity of reac- 

 tion products. 



Reversibility. Many catalytic processes have been shown to be 

 reversible, i.e., the same catalyst can influence the reaction in different 

 directions according to the concentration of the substances present. 

 Thus far we have only spoken of enzymotic cleavages; according to the 

 above it is to be expected that also synthetical processes can be produced 

 by enzymes. 



The first example of such a reaction was given by CROFT-HILL. S 

 He treated a 40 per cent dextrose solution with maltase at 30 C. for a 



1 Zeitschr. f. physiol. Chem., 57, 468, 1908. 



2 Hofmeister's Beitrage, 6, 68, 1905. 



3 Zeitschr. f . physiol. Chem., 9, 577, 1885. 



4 Pfliiger's Arch., 80, 470, 1900. 



5 Arbeit der Verdauungsdriisen, Wiesbaden, 1898, 33. 



6 Stade, Hofmeister's Beitrage, 3, 318, 1903; Engel, ibid., see Fromme, ibid., 7, 

 77, 1906. 



7 Immunochemie, 1907, 43. 



8 Journ. of chem. Soc., 73, 634, 1898. 



