Roles of hemoglobin and myoglobin

Heme, an iron-porphyrin complex, is the prosthetic group of many important proteins. The central role of hemoglobin and myoglobin in oxygen transport and storage was discussed in Chapter 28. Heme proteins or enzymes are involved in redox reactions (e.g., cytochromes) and participate in many oxidation reactions needed for synthesis of metabolically important compounds as well as for degradation and detoxification of waste products and environmental toxins. 

Iron plays a special role as a key constituent of hemoglobin and myoglobin. These proteins carry, hemoglobin, or store, myoglobin, oxygen in the hnman body and in those of other mammals. It is the iron atom, as Fe +, to which molecnlar oxygen binds in these proteins. 

Porphyrins are polyheterocyclic constituents of hemoglobin and myoglobin, the molecules that transport molecular oxygen in living systems (Section 26-8), of the cytochromes, which also play central roles in biological redox processes (Section 22-9), and of chlorophyll (Real Life 24-1), which mediates photosynthesis in all green plants. 

The abihty of iron to exist in two stable oxidation states, ie, the ferrous, Fe ", and ferric, Fe ", states in aqueous solutions, is important to the role of iron as a biocatalyst (79) (see Iron compounds). Although the cytochromes of the electron-transport chain contain porphyrins like hemoglobin and myoglobin, the iron ions therein are involved in oxidation—reduction reactions (78). Catalase is a tetramer containing four atoms of iron peroxidase is a monomer having one atom of iron. The iron in these enzymes also undergoes oxidation and reduction (80). 

They play very diverse and important roles such as 02 transport and storage (hemoglobin and myoglobin), catalytic dehydrogenation or oxidation of organic molecules... 

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. 

Pallet MS. Hemoglobin- and myoglobin-induced acute renal failure in rats role of iron in nephrotoxicity. Am J Physiol Renal Physiol 255 F539-544,1988. 

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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