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In biochemistry, non-heme iron proteins describe families of enzymes that utilize iron at the active site but lack heme cofactors. Iron-sulfur proteins, including those that are enzymes, are not included in this definition. Some non-heme iron proteins contain one Fe at their active sites, others have pairs of Fe centers:
Heme is a coordination complex "consisting of an iron ion coordinated to a tetrapyrrole acting as a tetradentate ligand, and to one or two axial ligands". [5] The definition is loose, and many depictions omit the axial ligands. [6]
Iron-binding proteins are carrier proteins and metalloproteins that are important in iron metabolism [1] and the immune response. [2] [3] Iron is required for life.Iron-dependent enzymes catalyze a variety of biochemical reactions and can be divided into three broad classes depending on the structure of their active site: non-heme mono-iron, non-heme diiron , or heme centers. [4]
Iron deficiency, or sideropenia, is the state in which a body lacks enough iron to supply its needs. Iron is present in all cells in the human body and has several vital functions, such as carrying oxygen to the tissues from the lungs as a key component of the hemoglobin protein, acting as a transport medium for electrons within the cells in the form of cytochromes, and facilitating oxygen ...
The human diet contains iron in two forms: heme iron and non-heme iron. Heme iron is usually found in red meat, whereas non-heme iron is found in plant based sources. Heme iron is the most easily absorbed form of iron. In those with hemochromatosis undergoing phlebotomy for treatment; restriction of dietary iron is not required.
Non-heme iron is mainly derived from plants and exist as iron(II) or iron(III) ions. [ 4 ] Iron is essential for more than 500 hemeproteins, the likes of which include hemoglobin and myoglobin , and account for 80% of iron usage. [ 1 ]
In hemoglobin, the iron is in one of four heme groups and has six possible coordination sites; four are occupied by nitrogen atoms in a porphyrin ring, the fifth by an imidazole nitrogen in a histidine residue of one of the protein chains attached to the heme group, and the sixth is reserved for the oxygen molecule it can reversibly bind to. [5]
Pappenheimer bodies are visible with a Wright and/or Giemsa stain. Confirmation of non-heme iron in the granules is made with a Perls' Prussian blue stain, and this atypical red blood cell is then known as a siderocyte. [5] Only the finding of ring (or ringed) sideroblasts characterizes Sideroblastic anemia.