Catalase assay

The complete incubation system contained isolated mitochondria resuspended in 0.25 M sucrose to a final concentration of 0.5 mg/ml protein. Light samples were exposed to an incandescent light source (a bank of 50 watt G.E. reflector bulbs) with an intensity of about 15 mW/cm for 2 hr. Six ml samples were incubated in a slowly shaking water bath at 34° C small aliquots were removed for catalase assays. Samples run in duplicate. 

Catalase is a marker peroxisomal enzyme. The degree of inhibition of all three catalases assayed was very similar among them. This effect can be used for quality control as the compound loses its selective cytotoxicity, the inhibiting capacity also diminishes... 

The first investigator to use buffered solutions for a catalase assay was S0rensen in 1909 (324) who found a pH optimum at about pH 7. Similar optimal pH values were reported by Michaelis and Pechstein (243), Bodan-sky (65), and Rona and Damboviceanu (292). The practice of using buffered solutions started to become more general with von Euler s work in 1920 (137). 

TABLE IV. Comparison of Manometric Catalase Assays with Respect to Activity Values Obtained... 

Advantages. The gasometric catalase assay methods can be used for any kind of biological material a purification of the enzyme is not required. The assay is independent of small amounts of peroxidase activity. It is fairly simple to perform, it is rapid, and it can be adapted to a continuous recording of the reaction. 

A second titration method used for catalase assays is based on the addition of an excess of acid KI to the reaction mixture followed by titration of the Ij produced with Na Oj solution. 

Not many assay methods obey equation (2) over a wide range and in some cases definite limits must be set in order to give a constant vidue of k For example, Sumner (30) limits the enzyme concentration in catalase assays to a 1.6-fold range. 

The electrode has not been used as much as the ultraviolet spectro-photometric method for routine catalase assays, and does not cover a sufficiently wide range of peroxide concentration to be suitable for studying the activity-substrate concentration relationship. The technique is suitable for simultaneous measurements of catalase activity and the catalase complex as described below. 

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