Effect of Sodium Dodecyl Sulfate on the Dissociation of Bovine Liver Catalase

Abstract

Native bovine liver catalase [EC 1.11.1.6] and catalase acetylated with N-acetylim-idazole (AI) both combined with sodium dodecyl sulfate (SDS) to form catalase-SDS complexes. The differences between native and acetylated catalase bound to SDS were investigated as regards enzymatic activity, absorption spectra, ORD and CD, sedimentation velocity and fluorescence spectra. It was found that the binding of SDS with both catalases depended on incubation time and SDS concentration, and that the acetylation of catalase had some protective effect on the denaturation of the molecule by SDS, which may be ascribed to a reduction of ionic interaction between SDS and the protein on acetylation. The native catalase was found to split into three smaller components on incubation with 1% SDS for 96 hr, whereas the acetylated catalase split into two smaller components. These smaller components were isolated by gel filtration through Sephadex G-100. The isolated components had estimated molecular weights of 60,000, 30,000, and 10,000–12,000 on the basis of SDS-polyacrylamide gel electrophoresis as well as gel filtration. The second component was not detected in the case of the acetylated catalase. The last component was the smallest which has ever been isolated from split molecules of catalase. Measurements of absorption spectra, ORD and CD as well as amino acid composition of some isolated components were carried out in this study.