Efficient Expression of Peroxidatic Activity of Catalase in the Coupled System with Glucose Oxidase—a model of Yeast Peroxisomes

Catalase functioned exclusively to degrade hydrogen peroxide in a reaction mixture containing methanol and hydrogen peroxide, while, when the enzyme was coupled with glucose oxidase, successful conversion of methanol to formaldehyde occurred at the optimized ratio of glucose oxidase to catalase: activity, 1.0 × 10 ^-3; number of molecules, 1.3; protein content, 1. These values in the coupled system were very similar to the ratio of alcohol oxidase to catalase in peroxisomes, one of the subcellular organelles from a methanol-assimilating yeast, Kloeckera sp. 2201, in which these enzymes were coupled to metabolize methanol efficiently. The presence of the optimum ratio in the coupled system in vitro was confirmed by the kinetic analysis of the expression of the peroxidatic activity of catalase coupled with glucose oxidase. Construction of the immobilized system of the coupled enzymes at the optimum ratio demonstrated that the oxidation of methanol through the peroxidatic function of catalase could be continuously and stably operated, the results indicating the usefulness of the system as a model of yeast peroxisomes. Thus, the coupled reaction with glucose oxidase brought out the latent function of catalase, which could not be expected in the system including only catalase.