Localization of Glucose Oxidase and Catalase Activities

The subcellular localization of glucose oxidase (EC 1.1.3.4) in AspergiUlus niger N400 (CBS 120.49) was investigated by (immuno)cytochemical methods. By these methods, the bulk of the enzyme was found to be localized in the cell wall. In addition, four different catalases (EC 1.11.1.6) were demonstrated by nondena-turing polyacrylamide gel electrophoresis of crude extracts of induced and noninduced cells. Comparison of both protoplast and mycelial extracts indicated that, of two constitutive catalases, one is located outside the cell membrane whereas the other is intracellular. Parallel with the induction of glucose oxidase, two other catalases are also induced, one located intracellularly and one located extracellularly. Furthermore, lactonase (EC 3.1.1.17) activity, catalyzing the hydrolysis of glucono-b-lactone to gluconic acid, was found to be exclusively located outside the cell membrane, indicating that gluconate formation in A. niger occurs extracellularly. The subcellular localization of glucose oxidase in As-pergillus niger has been a point of discussion. For a long time, the enzyme was assumed to be located intracellularly (14). This was further supported by ultrastructural studies by van Dijken and Veenhuis, who concluded that the enzyme was located in peroxisomes (20). Mischak et al. (13) showe