Porphyrin-containing proteins hemoglobins, human

Iron occurs in every mammalian cell and is vital for life processes. It is bound to various proteins and found in blood and tissues. The iron-porphyrin or heme proteins include hemoglobin, myoglobin and various heme enzymes, such as cytochromes and peroxidases. Also, it occurs in non heme compounds, such as ferritin, siderophilin, and hemosiderin. Hemoglobin, found in the red blood cells, is responsible for transport of oxygen to the tissue cells and constitutes about two-thirds (mass) of all iron present in the human body. An adult human may contain about 4 to 6 grams of iron. 

Iron, Fe a bioelement found in all living cells. The human body contains 4-5 g Fe, of which 75 % is in hemoglobin. In living organisms Fe occurs in the II and III oxidation states in higher animals it is stored bound to protein. It is transported in the blood as a complex with transferrin (see Siderophilins), from which it is transferred enzymatically to metal-ffee porphyrin molecules (see Heme iron). Non-heme iron (see) is also found in a number of compounds, e.g. Iron-sulfur proteins (see). The Fe metabolism of microorganisms is mediated by a group of natural products called Siderochromes (see). 

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