504 ENZYMES 



the number of milligrams of purpurogallin which would be 

 produced by i mgm. of the vacuum-dried preparation. This 

 number which is about 0-25 for well-pounded horse-radish 

 has been raised in the purest samples to over 3000. 



Practically nothing is known regarding the chemical nature 

 or mode of action of peroxidases. 



The view formerly expressed by Willstatter that horse- 

 radish was a nitrogenous glucoside containing over 30 per cent 

 of pentose and an equimolecular proportion of glucose has been 

 entirely modified owing to his obtaining more highly purified 

 preparations ; these latter are free from both carbohydrate 

 and protein, and contain only o-o6 per cent of iron and 0-027 

 of phosphorus, probably only present as impurities, but 

 contains from 9-37-1 3-57 per cent of nitrogen. 



Regarding the mechanism of the action of peroxidase, 

 Gallagher * has found that peroxidase prepared by precipita- 

 tion with alcohol is usually associated with aldehydic sub- 

 stances t and appears to have an oxide group of the type 

 Ri = O ; this group in conjunction with the ordinary peroxide 



grouping R^ \ gives rise to an oxidation potential higher 



than that possessed by either alone, and he suggests that the 

 first step in the oxidation process is the formation of a complex 

 of the type — 



/°\ 



Reagents Used for Detection of Oxidases and Peroxidases. 



{a) Oxidases — 



1. Guaiacum tincture (freshly prepared and dissolved in ab- 

 solute alcohol diluted with water) gives a deep blue coloration. 



2. One per cent a-naphthol in 50 per cent alcohol and 

 0-75 per cent p-phenylene diamine in the presence of a little 

 sodium carbonate give on addition of a drop of hydrogen 

 peroxide a deep blue colour. 



3. One per cent benzidine in 50 per cent alcohol, followed 



* Gallagher : " Biochem. Journ.," 1924, 18, 29. 



t The idea that peroxidases were aldehydes was first suggested by 

 Woker : " Ber. deut. chem. Gesells.," 1914. 47» 1024 ; 1917, 50, 672, 677. 



