Splitting of Catalase Molecule by Alkali Treatment

In 1938, Sumner and Gralén (1) reported that the molecule of bovine catalase with the sedimentation constant of 11.3 S was split into smaller components or subunits when the enzyme solution was made up to pH 9.9. In the resultant solution, they identified two components with sedimentation constants of 1.2 S and 4.5 S. The implication of this interesting observation has, however, been left unelucidated until now. Considering the importance of the phenomenon in clarifying the nature of catalase molecule, we repeated the experiment of Sumner and Gralén, extending the range of pH applied from 7.0 to 12.0. By measuring simultaneously the sedimentation pattern and enzymatic activity of the solution, it was revealed that the product of alkali splitting of catalase molecule was, in disagreement with the results reported by Sumner and Gralén, homogeneous and showed a sedimentation constant of 3.1 S. The splitting of the molecule proceeded to completion at pH 12.0, where the enzyme activity also disappeared completely. The changes in sedimentation pattern and catalase activity were found to be partially reversible, giving rise to two components, one showing a sedimentation constant of 5.8–6.4 S, and the other having a a sedimentation constant similar to that of native catalase. Described herein are the experimental results and some deductions drawn from them.