Cereal Chem 57:46 - 49.  |  VIEW ARTICLE
Studies of the Role of Ascorbic Acid in Chemical Dough Development. II. Partial Purification and Characterization of an Enzyme Oxidizing Ascorbate in Flour.

D. R. Grant and V. K. Sood. Copyright 1980 by the American Association of Cereal Chemists, Inc. 

Less than 20% of the ascorbic acid oxidase in a bread flour could be extracted with water or dilute salt solution. Soluble preparations containing up to 70% of the total activity of a flour suspension were obtained by extraction at room temperature with 75% saturated Na2SO4 solution at pH 8.3. Such extracts had high specific activity and contained a dialyzable component that absorbed strongly at 258 nm. Dialysis against water caused large losses of activity. Concentrated Na2SO4 solution stabilized the interaction between the dialyzable and the nondialyzable components. Ultracentrifugal analysis of the latter indicated a molecular weight of 21,000 in neutral dilute saline solution. When chromatographed on Sephadex G-100 columns in the presence of concentrated Na2SO4, the active species, which included the component absorbing at 258 nm, was eluted in the void volume. We postulate an oligomeric complex that dissociated into inactive monomeric species upon reduction of the ionic strength of the solution. Nitrate ion and halide ions, particularly fluoride, inhibited the enzyme. Calcium ion was stimulatory.