426 PRACTICAL ORGANIC AND BIO-CHEMISTRY 



Oxidases. 



A. Catalase. 



The measurement of catalase is effected by estimating volumetrically the 

 amount of oxygen produced. 



B. Peroxidases. 



The estimation of the activity of a peroxidase is most easily effected 

 colori metrically ; the colour produced may be estimated with a spectrophoto- 

 meter. 



If an insoluble precipitate is produced it can be filtered off and weighed, 

 or it can be centrifuged and its bulk measured in the centrifuge tube. 



The methods are so various and depend so much upon the particular 

 reaction suitable to the peroxidase that they must be referred to in the larger 

 text-books. * 



The indophenol reaction is very convenient as shown by Vernon. 1 



The indophenol which is insoluble and is deposited on the tissue is 

 dissolved by adding a known volume of alcohol (10 c.c.); after 25 minutes 

 the alcohol solution is filtered and compared colorimetrically with a standard 

 prepared by adding i part of the substrate to 200 parts of 50 per cent, 

 alcohol and sufficient bleaching powder (i part of *5 per cent, solution) to 

 give a maximum tint on standing (1-2 days). The colour of the standard 

 keeps for some weeks and then fades. The standard is kept in a sealed 

 tube, a known volume of the indophenol is put into a similar test tube and 

 diluted till the colours match. The colour varies from purplish pink to 

 violet, depending on the amount of alcohol present, and can be made to 

 match by adding water or alcohol. The colour is white with alcohol and 

 pink with water. 



1 J. Physiol., 42, 402. See p. 412. 



