Iron mobilisation

Biemond, P., Swaak, A.J.G., BiendorfF, C.M., and Kostner, J.F. (1986). Superoxide-dependent and independent mechanisms of iron mobilisation from ferritin by xanthine oxidase. Biochem. J. 239, 169-173. 

Ceruloplasmin is involved in copper storage and transport as well as in iron mobilisation and oxidation. Among the blue oxidases it is unique since it contains, in addition to the usual motif of a type 1 combined with the trinuclear cluster, two other type 1 coppers. Electron transfer occurs, however, only between five of the six copper ions since one of the type 1 centres is not catalytically relevant due to its too high redox potential. The redox potentials of the centres were determined and possible electron transfer pathways among the copper sites were discussed.101... 

Leyval, C. Berthelin, J. (1989). Interactions between Laccaria laccata-Agrobacterium radiobacter and beech roots influence on phosphorus, potassium, magnesium and iron mobilisation from minerals and plant growth. Plant and Soil, 117, 103-10. 

Ceruloplasmin, akin to Pirandello s Six Characters in Search of an Author, has long been a protein in search of a function. It is certainly involved in tissue iron mobilisation, since systemic iron loading is found in the tissues of patients with aceruloplasminaemia and other mutations of the ceruloplasmin gene. 

Crocidolite Leaching of iron from fibres, acellular In vitro Reactivity of iron-bound asbestos compared with iron mobilised from asbestos Mobilisation of iron from crocidolite by chelators such as citrate, nitrilotriace-tate or EDTA greatly enhances its redox actmty. This nmy lead to increased production of ROS. Lund and Aust (1991) Fe on or in crocidolite may be responsible for redox activity... 

Treeby M., Marschner H., Romheld V. Mobilisation of iron and other micronutrient cations from a calcareous soil by plant borne, microbial and synthetic chelators. Plant Soil 1989 114 217-226. 

The subject of this chapter will be the most important mechanisms by which microorganisms mobilise substrates. We will thereby focus on the mobilisation of nonliving food molecules, and will not deal with living food organisms. Besides organic compounds, we will also treat the biological mechanisms to acquire iron as the least bioavailable inorganic nutrient in many environments. 

Sinha (60,61) has suggested that humic and fulvic acids play a major role in mobilising iron and transporting it from the soil to plant roots. At the normal soil pH it is believed that iron bound by the fulvic acid is partially hydroxylated as Fe(OH)2 (62). These complexes interact with phosphate to give an organicmetallic phosphate which may be taken up by plants (60). It has been suggested that the entire humic-iron-phosphate complex is taken up by the roots of plants and not just the iron and phosphate (60, 63). Jorgensen (64) has observed that soil humates suppress the uptake of Pb2+ into plants it is possible that they will also suppress actinide concentration in plants. 

While a wide range of light-mediated transformations of iron are possible, it is important to place these transformations in perspective and assess the extent of their occurrence in natural aquatic systems. Within this context, evidence from field studies for light-mediated transformations of iron is reviewed in Sect. 4 and a brief discussion provided of the implications of these transformations to both iron bioavailability and contaminant mobilisation. 

There is a small amount of ferritin in the blood in balance with the iron stores. Iron is stored as ferritin (which sequesters iron in a nontoxic but readily mobilised form) and its aggregate, haemosiderin, in the cells of the liver, bone marrow and spleen. A measure of the state of iron stores is provided by the amount of ferritin in the serum (normally 20-300 mmol/1) and by the relationship of serum iron concentration (normally 10-30 mmol/1 reduced in iron deficiency) to the binding capacity of transferrin (normally 45-70 mmol/1 increased in iron deficiency). Ferritin is an acute-phase reactant and may be an inaccurate measure of iron stores in inflammatory states, e.g. rheumatoid arthritis. Recently developed techniques to measure the plasma level of soluble transferrin receptor (which is increased in iron deficiency but not by infection or inflammation) may help differentiate the anaenria of iron deficiency from that of chronic disease. 

McAlister, J.J., Smith, B.J. Curran, J.A. (2003) The use of sequential extraction to examine iron and trace metal mobilisation and the case hardening of building sandstone a preliminary investigation. Microchemical Journal 74, 5-18. 

About a quarter of total body iron is stored in macrophages and hepatocytes as a reserve which can be readily mobilised for red blood cell formation (erythropoiesis). This storage iron is mostly in the form of ferritin like bacterioferritin, a 24-subunit protein in the form of a spherical protein shell enclosing a cavity within which up to 4500 atoms of iron can be stored, essentially as the mineral ferrihydrite. Despite the water insolubility of ferri-hydrite, it is kept in solution within the protein shell, such that one can easily prepare mammalian ferritin solutions which contain 1 M ferric iron (i.e., 56 mg/ml ). Mammalian ferritins, unlike most bacterial and plant ferritins, have the particularity that they are heteropolymers, made up of two subunit types, H and L. Whereas H-subunits have a ferroxidase activity, catalysing the oxidation of two Fe " " atoms to Fe, L subunits appear to be involved in the nucleation of the mineral iron core once this has formed an initial critical mass, further iron oxidation and deposition in the biomineral takes place on the surface of the ferrihydrite crystallite itself (for a more detailed discussion, see Chapter 19). 

FIGURE 14.18 Representation of the role of ceruloplasmin in mobilising iron from reticuloendothelial cells. (From Heilman [Pg.295]

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