The Biological Activity and Physical State of Intracellular Catalase

Abstract

The conditions which had previously been used to characterize and distinguish the enzymatic activity of catalase before and after adsorption at the air-water interface were applied to the same enzyme before and after extraction from the mammalian erythrocyte. Intracellular catalase differs from the extracted enzyme in the following respects its specific activity is much lower; it is highly resistant to inactivation by heat; its activity is increased by pre-heating at 50-56[degree]C (heat activation); it is resistant to inactivation by u-v. In all these respects the intracellular enzyme shares the properties of the interfacially unfolded catalase in vitro, while the extracted enzyme behaves like the soluble catalase in vitro. The author advances the hypothesis that catalase exists within the cell reversibly adsorbed at some intra-cellular interface, such as that between oil and water phases, of sufficiently low interfacial tension to permit desorption into the rolled-up, soluble form, upon lysis of the cell.