Heme proteins and oxidation in fresh and processed meats - Oxidation in Foods and Beverages and Antioxidant Applications - page 90

Fig. 4.5 Valine at site E11 (68th residue) in wild-type sperm whale metMb cannot
hydrogen bond with water that is liganded to the iron atom of the porphyrin. Threonine at
E11 does form a hydrogen bond with liganded water increasing hemin affinity 25-fold.
Adapted from Hargrove et al., 1996.
ability of each Mb mutants to promote lipid oxidation. H97A readily promoted
lipid oxidation in washed cod at pH 5.7 while WT Mb was intermediate and
V68T was the weakest promoter of lipid oxidation (Grunwald and Richards,
2006b). These results suggest that hemin release is the primary mechanism by
which heme proteins promote lipid oxidation in washed fish muscle at pH 5.7.
Hemin readily decomposes preformed lipid hydroperoxides producing alkoxyl
Fig. 4.6 Histidine at site FG3 (97th residue) in wild type sperm whale Mb excludes
solvent from the heme crevice and also interacts with the heme-7-propionate. An alanine
substitution at site FG3 allows water to hydrate the proximal histidine decreasing hemin
affinity. Ala(FG3) cannot interact with the heme-7-propionate group which also
decreases hemin affinity. The proximal histidine is shown below the heme group. The
distal histidine is shown above the heme group. The PDB structure 1A6K was used to
prepare the image shown using PyMOL software.