Ferritin

Ferritin (FT ) ( Latin ferrum, iron '), and depot iron, is a protein complex that is found in animals, plants and bacteria, where it serves as a storage material for iron. In man, ferritin is mainly in the liver, spleen and bone marrow. In healthy individuals, about 20 % of the total iron is stored in ferritin. Mutations of the genes encoding for ferritin subunits can cause hereditary metabolic diseases (see table in text).

Although most ferritin is within the cells, the ferritin concentration in human blood serum is a meaningful measure of the total iron stores of the organism. The determination of ferritin is now routine in laboratory diagnostics, and has especially in the diagnosis of anemia and hemochromatosis a high priority.

Structure and occurrence

Ferritins are about 8 nanometers in size, filled with iron hydroxide oxide disc-like proteins, which are composed of 24 identical protein subunits (see picture). Subunits ( apoferritin ) have a length of about 150 to 160 amino acids in Bakterioferritin, 170 to 180 amino acids in the animal, and to about 200 amino acids in the plant ferritin. Together with the approximately 4000 iron atoms has a Ferritinkomplex in humans so that a mass of about 900 kDa.

Vegetable apoferritin is found in two isoforms in chloroplasts. Mammalian apoferritin forms three isoforms; in humans are localized predominantly intracellularly in these macrophages in the heart ( H), in the liver, spleen, bone marrow (L) and the mitochondria of the testis (MT ). Only a small proportion is extracellular ferritin in serum before, the iron loading corresponds relatively to that of the intracellular ferritin.

Biosynthesis and biological function

Iron ions in the cytosol bind to always existing latent mRNA coding for FTL and FTH and cause their activation and binding to ribosomes with the following translation. Lowering the level of iron in a particular aconitase loses its [ 4Fe -4S] cluster operates in the following as an iron regulatory protein (IRP ) and inhibits Ferritintranslation by binding to eisenresponsive elements (IRE) in the ferritin mRNA.

The functions of ferritin are oxidation of iron (II), the transport of iron (III) in the molecule inside structure of the mineral iron in the interior and this iron mobilization.

To fill the cavity of the ferritin iron, is poly ( rC ) binding protein -1 ( PCBP1 ) than chaperonin.

Mitochondrial ferritin can serve in mitochondria during pathological conditions as an additional iron stores. In addition to ferritin and hemosiderin hemoglobin are the main storage forms of iron in the organism (share 50 and 30% respectively ).

Laboratory diagnostics

Reference range

Conversion: 1 ng / ml = 1 ug / L

Infants:

• Cord blood 30-276 ng / ml
• 2nd - 3rd Week 90-628 ng / ml
• 1 month 144-399 ng / ml
• 2 months 87-430 ng / ml
• 4th month of 37-223 ng / ml

Children:

• 6 months - 15th Age of 7-142 ng / ml

Women:

Men:

Ferritin is too low

• Iron deficiency

Ferritin too high

• Hemochromatosis
• Tumor anemia
• Infection anemia
• Thalassemia