Immobilized catalase-containing yeast cells: Preparation and enzymatic properties

The cell of Saccharomyces cerevisiae previously induced for catalase (EC 1.11.1.6) activity were immobilized by entrapment of intact cells in acrylamide polymerized by γ irradiation (100 kR). Yeast cells showed an enhancement in catalase activity on entrapment, an effect similar to that observed on treatment with organic solvents like toluene. The cells pretreated with toluene, however, showed complete loss of catalase activity on entrapment. The entrapped enzyme exhibited a narrow pH optimum, reduced K_m for H₂ O₂ , and a decrease in thermostability. The temperature optimum of catalase was also decreased from 60 to 40°C on immobilization. A tenfold decrease in the activation energy was also observed. The enzyme in the entrapped cells was, however, stable toward inactivation by γ irradiation. Unlike the intact cells, the entrapped yeast cells did not have the ability to induce catalase.