A SPECTROSCOPIC STUDY ON THE HEAT INDUCED CHANGES OF GLUCOSE OXIDASE AT ACIDIC pH VALUES

The heat induced conformational and structural changes of glucose oxidase from Aspergillus niger at pH 5.0 and 4.0 were investigated using fluorescence spectroscopy. Experimental studies were conducted in buffer solution in the 25°C70°C temperature range at constant time. At both pH values, the phase diagram was linear, indicating the presence of two molecular species induced by thermal treatment. When thermally treating the glucose oxidase at pH 4.0, the denaturation process was faster than the one at pH 5.0, probably due to the release of cofactor FAD and molten globule formation. The quenching experiments using acrylamide and iodide revealed a more flexible conformation of glucose oxidase at higher temperatures, especially at pH 4.0.