Oxygen carriers, hemoglobin myoglobin

These superoxo complexes are relevant models for the naturally occurring oxygen carriers hemoglobin and myoglobin, which contain ferroprotoporphyrin IX as an active center in which the sixth axial postion is occupied by the imidazole moiety of histidine.17 They also intervene as primary oxygen adducts in enzymatic cytochrome P-450 oxygenases.18... 

Iron. Iron is ubiquitous in biological systems. It occurs in the hemopro-teins, including the oxygen carriers hemoglobin and myoglobin in a variety of electron carriers, including the cytochromes and cytochrome oxidase and in various enzymes that catalyze distinctly different reactions. In the Fe(III) oxidation state the metal can occur in a low-spin, S = i state or a high-spin, 5 = i state. There are a few examples of an intermediate or 5 = f state. 

Pancreatic ribonuclease Staphylococcal nuclease Peroxidases Glutathione peroxidase Cytochrome c peroxidase Oxygen carriers Myoglobin, hemoglobin Myohemerythrin, hemerythrin Hormone-binding proteins Uteroglobin Pre albumin Lectins... 

The two most important metalloprotein, other than hemoglobin and myoglobin are hemerythrins and hemocyanin which act as natural oxygen carrier. Hemocyanin is discussed in previous question. 

Many metals are essential to plant and animal life, although in many cases their role is uncertain. The list includes all the first-row transition metals except scandium and titanium, but only molybdenum and perhaps tungsten from the heavier transition metals. Table 16-1 lists several that are important in mammalian biochemistry. The importance of iron is obvious from the number of roles it plays, from oxygen carrier in hemoglobin and myoglobin to electron carrier in the cytochromes to detoxifying agent in catalase and peroxidase. 

Heme A porphyrin ring that has a Fe+ ion coordinately bound in the center of the molecule. Heme binds oxygen in hemoglobin and myoglobin and serves as an electron carrier in the cytochromes. 

Hemerythrin and myohemerythrin have roles as oxygen carriers in marine invertebrates, a function similar to that of the heme proteins hemoglobin and myoglobin in mammals and the copper-protein hemo-cyanin in mollusks and arthropods 1-7, 13). 

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