Abstact

We investigated the binding of epigallocatechin gallate (EGCG) to turkey hemoglobin A (Hb), noting that polyphenols have the capacity to inhibit oxidative deterioration in muscle foods mediated by endogenous hemoglobin. The addition of EGCG to MetHb resulted in covalently bound EGCG to Cys(130) of both alpha-chains. The crystal structure showed that each bound EGCG was located near the other and in the protein interior. Distances between the nearest phenol/phenolate of bound EGCG and the nearest iron atom of the heme moieties were 11.7-16.5 A. Antioxidative characteristics due to bound EGCG included decreases in both hemin dissociation and H(2)O(2)-mediated ferryl Hb formation, counterbalanced by increased Hb autoxidation. Bound EGCG less effectively inhibited oxyHb-mediated lipid oxidation compared to MetHb-mediated lipid oxidation. The mechanisms by which EGCG adduction affected oxidative characteristics of Hb are discussed, including electron transfer from bound EGCG to the heme, interactions with lipids, and effects of cross-linking on hemin affinity.