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Effect of pH on Structural Changes in Perch Hemoglobin that Can Alter Redox Stability and Heme Affinity |
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| Authors: | Mark P Richards Roman Aranda IV Cai He George N Phillips Jr |
| Institution: | 1. Meat Science and Muscle Biology Laboratory , Department of Animal Sciences, University of Wisconsin–Madison , Madison, Wisconsin, USA mprichards@ansci.wisc.edu;3. Department of Biomolecular Chemistry , University of Wisconsin–Madison , Madison, Wisconsin, USA;4. Meat Science and Muscle Biology Laboratory , Department of Animal Sciences, University of Wisconsin–Madison , Madison, Wisconsin, USA;5. Department of Biochemistry , University of Wisconsin–Madison , Madison, Wisconsin, USA |
| Abstract: | pH can be manipulated to alter the oxidative stability of fish-based foods during storage. X-ray diffraction was used to investigate the ability of reduced pH to cause structural changes in fish hemoglobins that lead to enhanced oxidative degradation. Decreasing pH from 8.0 to 6.3 and 5.7 created a large channel for solvent entry into the heme crevice of perch hemoglobin beta chains. The proton-induced opening of this channel occurred between site CD3 and the heme-6-propionate. Solvent entry into the heme crevice can enhance metHb formation and hemin loss, processes that accelerate lipid oxidation. Reduced pH also decreased the distance between Ile at E11 in one of the alpha chains and the ligand above the heme iron atom. This sterically displaces O2 and protonated O2 which increases metHb formation. These studies demonstrate that pH reduction causes structural changes in perch hemoglobin which increase oxidative degradation of the heme pigment. |
| Keywords: | rancidity lipid oxidation quality deterioration blood protein crystallography heme proteins hemin |