68 



BIOLOGICAL CHEMISTRY 



marked retarding influence than the other products of reaction. 

 The following table shows that such does occur.* 



TABLE XII 



The combination of enzyme with the substrate explains 

 the relation of the concentration of enzyme and substrate 

 (p. 65). When the enzyme is present in excess the amount 

 of combination will depend on the concentration of the 

 substrate, but when the substrate is present in excess the 

 amount of combination will depend on the concentration of 

 the enzyme. 



SURFACE CONDENSATION 



It is well known that finely divided platinum condenses 

 hydrogen, so that one volume of platinum absorbs many 

 volumes of hydrogen. The concentration of hydrogen must 

 therefore be equivalent to that of many atmospheres. Under 

 the influence of platinum hydrogen unites with oxygen, even 

 at moderate temperatures, so rapidly that the platinum soon 

 becomes heated to a red heat. 



If the enzyme causes a similar concentration of substrate 

 and water the rate of reaction may be considerably increased. 

 The increase in the rate of reaction will depend upon the 

 degree of concentration on the surface of the enzyme. 



The extent of surface on which condensation occurs will 

 be the factor that regulates the effect of concentration of the 

 enzyme on the rate of catalysis. 



The enzymes form colloidal solutions, thus the extent of 

 their surface is very great. In illustration of this we can 

 quote the following : "A sphere of gold one-tenth of a 



* E. F. Armstrong, Proc. Roy. Soc., 1904, vol. 73, p. 516; H. E. 

 Armstrong and E. F. Armstrong, ibid., 1907, B. vol. 79, p. 360. 



