DEAMIDATION-INDUCED FRAGMENTATION OF MAIZE ZEIN, AND ITS LINKED REDUCTION IN FATTY-ACID-BINDING CAPACITY AS WELL AS ANTIOXIDATIVE EFFECT

Zein lost its antioxidative effect in proportion to the degree of deam idation. Changes in molecular weight distribution of the protein fract ion by deamidation were examined by means of gel filtration with Sepha cry S-200 and SDS-electrophoresis in 12% polyacrylamide gel. The deami dation reaction (mild acid-hydrolysis by 0.05N HCl in 70% ethanol) was accompanied by fragmentation of zein subunits. Concomitantly, the sur face hydrophobicity as well as fatty acid-binding capacity decreased w ith progressed deamidation. There was a close correlation (r=0.98) bet ween the antioxidative effect and the fatty acid-binding capacity, but not the surface hydrophobicity. A large part of the antioxidative eff ect of zein is directly or indirectly attributable to its capacity of burying unsaturated lipid in the inter- or intra-molecular hydrophobic spaces in which the amide groups are intimately involved. Copyright ( C) 1996 Elsevier Science Ltd