Oxymyoglobin, oxidation

Herod et al. [50] has studied the kinetics and mechanism of oxyhemoglobin (Hb02) and oxymyoglobin (Mb02) oxidation by nitric oxide. At pH 7.0 the rate constants for these reactions were equal to 43.6+0.5 x 1061 mol 1 s 1 for Mb02 and 89 + 3 x 106 1 mol-1 s-1 for Hb02. It has been suggested that these reactions proceed via the formation of intermediate peroxynitrito complexes, which were rapidly decomposed to the Met-form of proteins, for example ... 

Herold, S., Exner, M., Nauser,T., Kinetic and mechanistic studies of the NO -mediated oxidation of oxymyoglobin and oxyhemoglobin, Biochemistry 40 (2001), p. 3385-3395... 

As the distance extends to 400 m, oxidation of some of the glycogen occurs, producing about 25% of the ATP generated in this event. Some of the oxygen required comes from oxymyoglobin that is present in the muscle (see below). 

The second reaction and certainly the major route for the destruction of nitric oxide in vivo is the fast and irreversible reaction with oxyhemoglobin (Hb) or oxymyoglobin to produce nitrate. 

NOTE It is extremely critical to perform all steps at 4°C to minimize oxidation of ferrous deoxy- or oxymyoglobin to metmyoglobin, especially when using a buffer at pH 5.6, the typical post-mortem skeletal muscle pH. 

In both pigments, the iron is in the ferrous form upon oxidation to the ferric state, the compound becomes metmyoglobin. The bright red color of fresh meat is due to the presence of oxymyoglobin discoloration to brown occurs in two stages, as follows ... 

Y9. Yusa, K., and Shikama, K., Oxidation of oxymyoglobin to metmyoglobin with hydrogen peroxide Involvement of ferryl intermediate. Biochemistry 26,6684-6688 (1987). 

O Grady, M.N., Monahan, F.J., and Brunton, N.P., Oxymyoglobin oxidation and lipid oxidation in bovine muscle mechanistic studies, J. Food Sci., 66, 386, 2001. 

From these structural and chemical features considered necessary to mimic oxyhemoglobin or oxymyoglobin, there are at least two minimum requirements that any realistic models must satisfy (1) formation of a five-coordinate heme precursor having a proximal base (imidazole, pyridine and so on) and (2) limitation of pathways that lead to irreversible oxidation. 

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