STUDY OF THE ENZYME ASCORBATE OXIDASE BY SMALL-ANGLE NEUTRON-SCATTERING

We report a study of the large scale structure of the ''blue'' copper enzyme ascorbate oxidase by small angle neutron scattering. The enzyme has been extracted from zucchini and studied in solutions of two diff erent preparations. Contrast variation method was used by performing t he measurements in water, heavy water and mixtures of H2O-D2O. Our dat a show that, at least at the concentrations used here, the gyration ra dius of the enzyme is about 34 Angstrom; with such a value our analysi s is most consistent with a value of 70 KDa for the molecular weight o f ascorbate oxidase in the conditions of our experiment. This is in co ntrast to the generally accepted value of 140 KDa, obtained by other t echniques at high concentrations (e.g. greater than 2 mg ml(-1)). The possible origins of such a discrepancy are discussed.