Myoglobin in muscle

Most of the iron in the body is in the form of haemoglobin in red blood cells and myoglobin in muscle. The remainder is in the liver, spleen and other tissues. Haemoglobin is essential for the proper functioning of every organ and tissue of the body. Iron has a rapid turnover rate in the chicken therefore, it must be provided in a highly available form in the diet on a daily basis. Iron deficiency can result in microcytic, hypochromic anaemia in poultry. Any internal infection such as coccidiosis can also interfere with iron absorption and lead to a deficiency. 

Haem is bound to proteins to make haemoglobin (in blood) and myoglobin (in muscle). The hydrophilic carboxy-late groups stick out into the surrounding medium, while the majority of the molecule is embedded in a hydrophobic cleft in the protein, lined with amino acids such a leucine and valine. The octahedral coordination sphere of the iron(II) is completed with a histidine residue from the protein and an oxygen molecule. 

Figure 25.8 Oxygen dissociation curves for haemoglobin and myoglobin, showing how haemoglobin is able to absorb O2 efficiently in the lungs yet transfer it to myoglobin in muscle tissue.

D. Diffusion to mitochondria within cells (may be facilitated by myoglobin in muscle cells)... 

The most obvious function of iron is in the haem of haemoglobin, the oxygen-carrying protein in red blood cells, and myoglobin in muscles. Haem is also important in a variety of enzymes, including the cytochromes (section 3.3.1.2), where it is the coenzyme in oxidation and reduction reactions. A number of enzymes also contain non-haem iron (i.e. iron bound to the enzyme other than in haem), which is essential to their function. 

Ribbon views of proteins with varying amounts of helices and pleated sheets. Immunoglobulin, an antibody, is made up almost entirely of pleated sheets (magenta). Myoglobin, which stores oxygen in muscle tissue, is composed of about 70% helix (blue). G-Actin, a component of muscle protein fibers, is a complex mixture of helices and pleated sheets. Regions with no specific secondaiy stmcture are shown in orange. 

Cytochrome c is a heme containing protein which occurs in muscle at lower concentrations than does myoglobin. It was demonstrated some time ago (18) that oxidized cytochrome c reacts with gaseous nitrite oxide to produce a nltrosyl compound. Recent work (19, 20, 21) has examined the reactions of cytochrome c with nitrite and the contribution of the product formed to cured meat color in considerably more detail. The general conclusion is that even at the pH normally encountered in meat, the reaction can take place in the presence of ascorbic acid but probably does not affect meat color because of the unstable nature of the reaction product and the low concentration. 

During periods of acute psychosis, some patients exhibit so much muscular activity that they develop muscular destruction with the muscle product myoglobin in urine, which produces acute renal failure (16). Some muscle destruction may be due to involuntary muscle activity induced by the drug, while some may be due to the struggles of the agitated patient. In the latter case, the use of restraints may worsen the situation. 

B. Chance, S. Nioka, J. Kent, K. McCully, M. Fountain, R. Greenfeld, and G. Holtom. Time-resolved spectroscopy of hemoglobin and myoglobin in resting and ischemic muscle. Anal. Biochem., 174 698-707, 1988. 

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