Hemoglobin iron protoporphyrin

Cytochromes were first named and classified on the basis of their absorption spectra (Figure 21.9), which depend upon the structure and environment of their heme groups. The b cytochromes contain iron—protoporphyrin IX (Figure 21.10), the same heme found in hemoglobin and myoglobin. The c cytochromes contain heme c, derived from iron-protoporphyrin IX by the covalent attachment of cysteine residues from the associated protein. UQ-cyt c... 

Iron protoporphyrin IX (heme) is found in the b-type cytochromes and in hemoglobin and myoglobin. In heme c, cysteine residues of the protein (R) are attached covalently by thioether links to the two vinyl (—CH=CH2) groups of protoporphyrin IX. Heme c is found in the c cytochromes. In heme A, which is found in the a cytochromes, a 15-carbon isoprenoid side chain is attached to one of the vinyls, and a formyl group replaces one of the methyls. 

In iron deficiency anemia, Zn2+ may be used instead of iron by ferro-chelatase in the biosynthesis of heme. Red blood cell lysates in such instances contain increased quantities of Zn-hemoglobin. In addition, red cells from iron-deficient patients also contain increased amounts of protoporphyrin IX. Zinc-hemoglobin and protoporphyrin IX determinations are thus used in the diagnosis of iron deficiency anemia. 

In iron deficiency anemia, red blood cells contained increased quantities of Zn-hemoglobin and protoporphyrin IX. 

The prosthetic group of cytochrome b is the same as that of hemoglobin, iron(II)-protoporphyrin IX. It has the lowest redox potential of the respiratory chain C, and therefore lies between ubiquinone and C.c. C.b, a dimeric protein (M, 60,000) with 1 heme group per monomer, is very firmly bound to the mitochondrial membrane, and can only be extracted with detergents. Its central iron atom, like that of C.c. is not autooxidizable and does not react with CO or cyanide. There is evidence that C.b exists in two forms, C.6k and b, which have different redox potentials. C.b is believed to function in the transfer of energy during electron transport. 

The insertion of iron into protoporphyrin gives rise to the iron branch of the biosynthetic chain (Figs. lA and IB). Iron protoporphyrin or its modifications are the prosthetic or active groups of the cytochromes, of peroxidase, of catalase, and of hemoglobin. 

The prosthetic group of the following heme proteins is iron protoporphyrin Hemoglobins (red cell and muscle), catalase, peroxidase, cytochrome b. 

In certain polychaetes, the worms contain a hemoglobin called chloro-cruorin dissolved in the hemolymph stream which has a greenish color in its oxygenated form. Studies by Fischer and co-workers have shown that the porphyrin it contains is an iron protoporphyrin modified at one of the vinyl groups. In the 2-position of the side chain (Fig. 3) it contains a formyl group in place of a vinyl group. 

The common prefix hem-, in these names does not derive from the presence of heme (iron protoporphyrin IX), which occurs only in hemoglobin, but from the Greek word for blood. 

Recently, a novel physical method for rapid and sensitive malaria detection in blood has been developed [46-50]. This method— ultraviolet LD MS—is based on the detection of heme (iron protoporphyrin) in blood as a qualitative and quantitative malaria biomarker, both in vitro [46] and in vivo [49,50]. In infected erythrocytes, the parasite sequesters heme from digested hemoglobin in a molecular crystal (malaria pigment or hemozoin). LDMS detects only heme from hemozoin in parasite-infected blood, and not heme, bound to hemoglobin... 

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