Hemosiderin properties

Finally, animal, plant and microbial tissues have been shown to contain the iron storage protein ferritin. The animal protein has been extensively studied, but the mechanism of iron binding has not been completely resolved (29). Animal tissues contain, in addition, a type of granule comprised of iron hydroxide, polysaccharide and protein. The latter, called hemosiderin, may represent a depository of excess iron (30). Interestingly, a protein with properties parallel to those of ferritin has been found in a mold. Here the function of the molecule can be examined with the powerful tools of biochemical genetics (31). 

The problems to be solved are listed hereafter the first problem is the lack of data concerning the exact proportions of low-molecular weight iron complex, ferritin-bound iron and hemosiderin-bound iron (54). However, transverse NMRD profiles of iron-loaded tissues indicate that the transverse relaxation is essentially caused by ferritin, because of the linearity between I/T2 and Bq, which is a fingerprint of ferritin-induced relaxation. The relaxation properties of hemosiderin are less understood. If the proportion of ferritin and hemosiderin is not the same in all of the studied tissues, the correlation between the relaxation properties and the total iron concentration could be affected. 

Most aspects of intermediary metabolism require essential trace elements in the form of metalloenzymes that have a range of catalytic properties. Specific metalloproteins are required for the transport and safe storage of very reactive metal ions, such as Fe or Cu. Examples are metaUo-thionein (Cu, Zn), transferrin, ferritin and hemosiderin (Fe), and ceruloplasmin (Cu). 

Deferoxamine is isolated as the iron chelate from Streptomyces pilosus and is treated chemically to obtain the metal-free ligand. Deferoxamine has the desirable properties of a remarkably high affinity for ferric iron K = 10 M ) coupled with a very low affinity for calcium K =10 M" ). Studies in vitro have shown that it removes iron from hemosiderin and ferritin and, to a lesser extent, from transferrin. Iron in hemoglobin or cytochromes is not removed by deferoxamine. 

PROPERTIES OF FERRITIN AND HEMOSIDERIN PRESENT IN HEALTHY BRAIN TISSUE... 

The above-presented properties of brain ferritin and hemosiderin suggest a different metabolism of iron in the brain and in organs such as the liver. As the H-ferritin subunits are involved more than L subunits in taking up and possibly also in releasing iron from ferritin, the significantly higher H/L ratio in the brain may possibly point to a higher turnover of iron in the brain [22]. 

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