Myoglobin iron content

Q5 The average diet in the United Kingdom contains approximately 15 to 20 mg of iron only about 10% of this is absorbed. The main iron content of the diet is haem iron derived from the haemoglobin and myoglobin in red meat, and this is the form of iron which is most readily absorbed. Non-haem iron, for example that derived from cereal products, is less well absorbed. The majority of iron absorption occurs in the duodenum and first part of the jejunum. Non-haem iron absorption is very variable, and some types of food, such as bran and egg yolk, limit its absorption. Gastric acidity helps to keep iron in the ferrous state, which is more easily absorbed than the ferric form. Iron absorption is increased when iron stores are low and when there is increased erythropoietic activity. 

The iron content of the body is 4—5g. Most of it is present in the hemoglobin (blood) and myoglobin (muscle tissue) pigments. The metal is also present in a number of enzymes (peroxidase, catalase, hydroxylases and flavine enzymes), hence it is an essential ingredient of the daily diet. The iron requirement depends on the age and sex of the individual, it is about 1.5-2.2 mg/day. Iron supplied in the diet must be in the range of 15 mg/day in order to meet this daily requirement. The large variation in intake can be explained by different extents of absorption of the various forms of iron present in food (organic iron compounds vs simple... 

The predominating form of iron in animal tissues is haem (particularly myoglobin and haemoglobin). In egg white, iron is bound in conalbumin, and in the yolk to phosphoprotein phosvitin. Milk contains the iron metaUoprotein lactoferrin and part of the iron is bound to casein. Conalbumin and lactoferrin are structurally similar to serum transferrin. In plants, iron is bound in various complexes, especially with phytic acid, aUphatic hydroxycarboxyhc acids, aminocarboxyhc acids, thiols, phenolic substances, nucleotides, peptides and proteins. The iron content in selected foods is shown in Table 6.8. Foods rich in iron are offal dishes, meat, eggs, pulses, tea and cocoa. Moderate amounts of iron are found in fish, poultry, cereals, spinach, parsley and nuts. Low levels of iron are present in milk, dairy products, fats and oils, potatoes and most fruit. 

The molecular weight of myoglobin was found to be 16,850 by osmotic pressure measurements (Roche and Vieil, 1940). Sedimentation equilibrium studies gave a molecular weight in the range of 16,900 to 17,600 (Poison, 1939a). The iron content of myoglobin is 0.345% (Theorell, 1932). Thus there can only be one heme per molecule. 

The PDOS of the iron in deoxy- and CO-myoglobin and of myoglobin with different degrees of water content was also determined by Achterhold et al. [112, 113]. They found that the modes with an energy larger than 3 meV (24 cm ) are harmonic at physiologically relevant temperatures. Those below 3 meV exhibit a... 

The total amount of iron in the body of an adult is about 3-5 g. The highest concentrations are found in the blood (haemoglobin), liver and spleen (ferritin and homosiderin) lower concentrations are in the kidney, heart and skeletal muscle (myoglobin). The concentration of iron in the pancreas and brain is about 2-10 times lower than the content of the Hver or spleen. A list of the organic compounds of iron is given in Table 6.7. 

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