Photometric determination of catalase activity.

Catalase activity may be measured quantitatively by the method of von Euler and Josephson (1) by allowing the enzyme solution to react with hydrogen peroxide for varying periods of time and measuring the excess peroxide remaining by titration with potassium permanganate. The similarity of this titration procedure to the assay of ascorbic acid by titration with 2:6-dichlorophenolindophenol suggested to the authors the possibility of measuring catalase activity photometrically (in a manner similar to the photometric estimation of vitamin C) by addition of an excess quantity of potassium permanganate and subsequent photometric measurement of the color. This procedure has been found to be practical and rapid. It gives reproducible results and, by photometric means, obviates the human error in reading the end-point of the potassium permanganate. As both hydrogen peroxide and potassium permanganate in the present procedure are used in the same concentrations as in the conventional von Euler and Josephson method, compounds that inhibit catalase such as HCN should have no different effect in this procedure from that in the conventional one. Apparatus and Reagents-The photometric determination of catalase activity may be carried out with any standard calorimeter or spectrophotometer.’ The reagents required for this measurement are as follows. Hydrogen peroxide (approximately 0.01 N) in phosphate buffer at pH 6.8. Use 5.67 ml. of 3 per cent hydrogen peroxide per liter. Potassium permanganate (approximately 0.005 N) ; 0.158 gm., made to 1 liter with distilled water. A solution of diluted cat,alase enzyme. For our study, a 1: 2500 catalaseSarett2 solution was used. Sulfuric acid (5 N); 142 ml. of concentrated sulfuric acid (sp. gr. 1.84) made to 1 liter with distilled water.