Properties of azide-catalase

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Abstract
Catalase combined reversibly with one molecule of azide/Fe atom of catalase hematin. As in the case of free catalase, the hematin Fe of azide-catalase was trivalent. Azide-catalase resembled free catalase in color, absorption spectrum, magnetic susceptibility, and resistance to reducing agents (Na2S2O4). On addition of H2O2 to azide-catalase, the color turned from greenish brown to red and the absorption band in the red was replaced by 2 bands at 587 and 559 m[mu]. This compound now contained Fe in the divalent state since it was stable only in absence of O2, rapidly reoxidizing to the original azide-catalase; reacted with CO forming a well defined compound which was more stable in air; CO inhibited the decomposition of H2O2 and this inhibition was abolished by light; cyanide did not displace the azide, as it did from the ferric azide-catalase. The close relationship between the properties of azide-catalase and free enzyme suggested that catalytic decomposition of H2O2 by catalase involved a cyclical reduction and oxidation of its Fe, estab-lished for azide-catalase.