A Reduced Activity of Catalase as a Basis for Light Dependent Methionine Sensitivity of a Chlamydomonas reinhardtii Mutant

Abstract

Pre-illumination of methionine-supplemented medium enhanced the inactivation of the light dependent methionine sensitive mutant cells of Chlamydomonas reinhardtii and, to a lesser extent, the wild-type cells, confirming that the photodamage is due to production of toxic produces) in the medium. Exogenously added catalase protected the mutant cells from growth inhibition. Starch gel electrophoresis showed lower catalase activity in the mutant cells than the wild type. Catalase activity which was followed by measuring O₂ evolution after the addition of H₂O₂ to the cell suspensions was consistently lower in the mutant than the wild type. The results indicate that light sensitivity in the presence of methionine expressed by this mutant is due to reduced activity of catalase.