No abstract

Catalase (hydrogen peroxide:hydrogen-peroxide oxidoreductase, EC 1.11.1.6) occurs in almost all aerobically respiring organisms and in part serves to protect cells from the toxic effects of hydrogen peroxide. The subcellular location of liver catalase is restricted to the peroxisomes, and the enzyme is probably incorporated into these organelles during their biogenesis (1). The properties of catalase have been reviewed by numerous authors including Deisseroth and Dounce (2) and Schonbaum and Chance (3). The overall reaction catalyzed by the enzyme can be written as ROOH + HQOH = QO + ROH + H20, [1] where R is H or an alkyl or acyl group and HQOH is a twoelectron donor in which Q is 0, C=O, or H(CH2)nCH (n = 1, 2, or 3). This reaction proceeds by two steps: (i) oxidation ofthe enzyme (E) by a peroxide E-H20 + ROOH = E-O + ROH + H20, [2] apocatalase I and (ii) oxidation of the substrate E-O + HQOH = E-H20 + QO.

No abstract

No abstract

Most of the amino acid side chains of beef liver catalase were clearly identifiable in the 2.5 R resol.ution electron density map and are in good agreement with the sequence (W. A. Schroeder et al., Arch. Biochem. Biophys. 131, 653-655, 1969). Thetertiary structure of one subunit consists of a large antiparallel S-pleated sheet domain with helica~ insertions followed by a smaller domain containing four ci:helices.