STUDY OF THE NEW ELECTRON-TRANSFER MEDIATORS IN GLUCOSE-OXIDASE CATALYSIS

The steady-state oxidation of glucose oxidase from Aspergillus niger b y phenothiazines, phenoxazines, Wurster's salts, dithia- and tetrathia aromatic compounds, and nickelocene was investigated spectrophotometri cally and electrochemically. At pH 7.0 the determined oxidation rate c onstants (TN/K(m)) vary in the range 10(3) to 10(8) M-1 . s-1. For phe nothiazines, phenoxazine and Wurster's salts oxidation constants depen d on the redox potential of the electron acceptors, and results were i nterpreted in the framework of the outer sphere electron transfer theo ry (Marcus and Sutin, Biochim. Biophys. Acta, 811 (1985) 265). The int erpretation of the kinetic results concerning thiaaromatic compounds a nd metallocenes are complicated due to complex formation with the enzy me active center and aggregation of their oxidized form in buffer solu tion.