Catalase

This chapter focuses on catalase that was recognized as being widely distributed in nature by O. Loew although the H2O2-cleaving activity of various tissues had already been described in 1819 by Thénard and erroneously considered to be a general property of all enzymes by Schönbein. The enzyme contains 4 ferriprotoporphyrin groups per molecule, which corresponds to a protohaem content of 1.1 % and an iron content of 0.09 %. The catalase activity of tissues varies greatly; it is highest in liver and kidney, and low in connective tissue. The physiological function of catalase is still obscure, although various theories have been put forward. Catalase activity can be measured by following either the decomposition of H2O2 or the liberation of O2. The kinetics of catalase does not obey the normal pattern. Catalase is applied in biochemistry and hematology, and occasionally in clinical chemistry. In the ultraviolet range H2O2 shows a continual increase in absorption with decreasing wavelength.