472 ENZYMES 



5. PARALYSERS. 



Amongst substances having a retarding effect on the 

 activity of enzymes may be mentioned inorganic substances 

 such as mercuric chloride or cyanide, arsenious oxide, sul- 

 phuretted hydrogen, ozone, and organic compounds such as 

 chloroform, chloral, formaldehyde, hydrocyanic acid, phenyl- 

 hydrazine, aniline, alcohol, etc.; the influence of these sub- 

 stances on different enzymes varies considerably ; thus, for 

 example, alcohol usually acts as a paralyser, but on lipase 

 it has a stimulating effect. 



The majority of the substances included in the above list 

 also act as poisons to colloidal solutions of metals ; the 

 peculiar phenomenon of the recovery of metallic colloidal 

 solutions from poisoning by hydrocyanic acid, is also met 

 with in the case of the enzymes, and is likewise attributed to 

 the oxidation of the poison. 



The mechanism of these toxic actions is as yet unexplained ; 

 it is assumed that some form of chemical combination between 

 the paralyser and the substrate enzyme or activator takes 



place.* 



6. RADIATION. 



With regard to the action of light rays on enzymes it ap- 

 pears, according to lodlbauer and v. Tappeiner,f that there 

 exist two distinct kinds of action : — 



{a) Those produced by ordinary light in the presence of 

 oxygen, and {b) those produced by ultra-violet light indepen- 

 dently of oxygen. 



The destructive action which has resulted from exposure 

 to bright sunlight therefore appears to be dependent on the 

 presence of oxygen, and is greatly increased by the presence 

 of fluorescent substances, such as eosin, quinoline red, etc. J 

 It is most destructive at the optimal reaction. § 



It was first shown by Green || that ultra-violet light de- 



* Cf. Loewenhart and Kastle : " Amer. Journ. Chem.," 1903, 29, 397, 



563. 



t lodlbauer and v. Tappeiner : " Deut. Archiv. Klin. Med.," 1906. 



I Tappeiner : " Biochem. Zeit.," 1908, 8, 47. 

 § See Pincussen : id., 1923, 134, 459. 



II Green : " Trans. Roy. Soc. Lond.," 1897, 188, 167. 



