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Query: UNIPROT:P02794 (ferritin)
 17,525 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

On account of its easy access in aqueous solution to the two states ferrous (FeII) and ferric (FeIII), iron is ideally suited for the activation of molecular oxygen. It is, therefore, logical to seek links between the normal and pathological metabolism of iron and oxygen activation. The pathways of intracellular iron metabolism require changes in the oxidation state of iron both in its deposition in the storage form, ferritin, and in its mobilization from the storage form and use in the cell. Evidence is presented which shows that iron oxidation and deposition in ferritin involves activation of molecular oxygen with formation of a stable peroxo-complex as an intermediate in which the oxygen is bound between two iron atoms attached to adjacent polypeptide chains. The release of iron from ferritin is thought to involve reduction by a flavin, which is associated with the protein, and serves as a cofactor being alternately reduced by NADH or NADPH and oxidized by iron(III). The nature of the low-molecular-weight iron complex which serves to transfer storage iron to transferrin and to supply iron for intracellular use remains to be established. The consequence of excessive iron overload can be rationalized on the basis of oxidative free-radical reactions which provoke lesions typical of deregulated oxygen activation. In some cases these pathological defects can be reversed by iron chelators. Progress in the development of chelation therapy for iron overload are reviewed.
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PMID:Interactions between iron metabolism and oxygen activation. 25 65

The distribution of cytochrome b5 reductase in rat liver microsomes purified by density gradient centrifugation was studied using anti-cytochrome b5 reductase/anti-ferritin hybrid antibodies labeled with ferritin. Electron micrographs show that the outer surface and the polar cap of tangential sections of essentially all vesicles derived from endoplasmic reticulum are specifically marked with a few ferritin grains which are not localized in large patches but arranged randomly. This finding was correlated with morphometrical and biochemical measurements. The results, supporting our earlier investigations, suggest that cytochrome b5 reductase may be clustered at the most in very small assemblies consisting of a few molecules which, in turn, are statistically uniformly distributed over the total membrane system.
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PMID:Immunohistological studies on the distribution of cytochrome b3 reductase in rat liver microsomes. 34 93

NADH-FMN oxidoreductase has been proposed as an enzyme involved in the release of iron from ferritin. The effects of riboflavin and/or iron deficiencies and of dietary allopurinol on the activities of this enzyme and on the iron contents of liver, kidney and duodenum were investigated. Allopurinol, a xanthine oxidase inhibitor, did not affect organ enzyme activities nor iron contents. Riboflavin-deficient rats and iron-deficient rats both had significantly lower organ enzyme activities and iron contrnts than controls. Organ enzyme activities and iron contents of rats fed a diet deficient in both iron and riboflavin were significantly lower than those of controls. After dietary iron and/or riboflavin repletion, organ enzyme activities and iron contents increased. Rats fed an irons-overload diet had enzyme activities similar to that of controls, but organ iron contents were significantly increased over those of controls. Effects of riboflavin and/or deficiencies in rats on NADH-FMN oxidoreductase activities and iron contents of liver, kidney and duodenum appeared to be reversible by riboflavin and/or iron supplementation. The data support the view that NADH-FMN oxidoreductase may be a controlling enxyme in iron release from ferritin.
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PMID:NADH-FMN oxidoreductase activity and iron content of organs from riboflavin and iron-deficient rats. 85 41

The iron storage protein, ferritin, represents a possible source of iron for oxidative reactions in biological systems. It has been shown that superoxide and several xenobiotic free radicals can release iron from ferritin by a reductive mechanism. Tetravalent vanadium (vanadyl) reacts with oxygen to generate superoxide and pentavalent vanadium (vanadate). This led to the hypothesis that vanadyl causes the release of iron from ferritin. Therefore, the ability of vanadyl and vanadate to release iron from ferritin was investigated. Iron release was measured by monitoring the generation of the Fe(2+)-ferrozine complex. It was found that vanadyl but not vanadate was able to mobilize ferritin iron in a concentration dependent fashion. Initial rates, and iron release over 30 minutes, were unaffected by the addition of superoxide dismutase. Glutathione or vanadate added in relative excess to the concentration of vanadyl, inhibited iron release up to 45%. Addition of ferritin at the concentration used for measuring iron release prevented vanadyl-induced NADH oxidation. Vanadyl promoted lipid peroxidation in phospholipid liposomes. Addition of ferritin to the system stimulated lipid peroxidation up to 50% above that with vanadyl alone. Ferritin alone did not promote significant levels of lipid peroxidation.
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PMID:Tetravalent vanadium releases ferritin iron which stimulates vanadium-dependent lipid peroxidation. 164 80

The oxidase reaction of lipoamide dehydrogenase with NADH generates superoxide radicals and hydrogen peroxide under aerobic conditions. ESR spin trapping using 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) was applied to characterize the oxygen radical species generated by lipoamide dehydrogenase and the mechanism of their generation. During the oxidase reaction of lipoamide dehydrogenase, DMPO-OOH and DMPO-OH signals were observed. The DMPO-OOH signal disappeared on addition of superoxide dismutase. These results demonstrate that the DMPO-OOH adduct was produced from the superoxide radical generated by lipoamide dehydrogenase. In the presence of dimethyl sulfoxide, a DMPO-CH3 signal appeared at the expense of the DMPO-OH signal, indicating that the DMPO-OH adduct was produced directly from the hydroxyl radical rather than by decomposition of the DMPO-OOH adduct. The DMPO-OH signal decreased on addition of superoxide dismutase, catalase, or diethylenetriaminepentaacetic acid, indicating that the hydroxyl radical was generated via the metal-catalyzed Haber-Weiss reaction from the superoxide radical and hydrogen peroxide. Addition of ferritin to the NADH-lipoamide dehydrogenase system resulted in a decrease of the DMPO-OOH signal, indicating that the superoxide radical interacted with ferritin iron.
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PMID:Mechanisms of generation of oxygen radicals and reductive mobilization of ferritin iron by lipoamide dehydrogenase. 165 85

The role of iron in allyl alcohol-induced lipid peroxidation and hepatic necrosis was investigated in male NMRI mice in vivo. Ferrous sulfate (0.36 mmol/kg) or a low dose of ally alcohol (0.6 mmol/kg) itself caused only minor lipid peroxidation and injury to the liver within 1 h. When FeSO4 was administered before allyl alcohol, lipid peroxidation and liver injury were potentiated 50-100-fold. Pretreatment with DL-tocopherol acetate 5 h before allyl alcohol protected dose-dependently against allyl alcohol-induced lipid peroxidation and liver injury in vivo. Products of allyl alcohol metabolism, i.e. NADH and acrolein, both mobilized trace amounts of iron from ferritin in vitro. Catalytic concentrations of FMN greatly facilitated the NADH-induced reductive release of ferritin-bound iron. NADH effectively reduced ferric iron in solution. Consequently, a mixture of NADH and Fe3+ or NADH and ferritin induced lipid peroxidation in mouse liver microsomes in vitro. Our results suggest that the reductive stress (excessive NADH formation) during allyl alcohol metabolism can release ferrous iron from ferritin and can reduce chelated ferric iron. These findings provide a rationale for the strict iron-dependency of allyl alcohol-induced lipid peroxidation and hepatotoxicity in mice in vivo and document iron mobilization and reduction as one of several essential steps in the pathogenesis.
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PMID:NADH-dependent reductive stress and ferritin-bound iron in allyl alcohol-induced lipid peroxidation in vivo: the protective effect of vitamin E. 173 Jan 48

Interactions of doxorubicin (DX) with the cardiolipin-dependent cytochrome c oxidase have been examined by using pig heart submitochondrial particles (SMP). A progressive and irreversible loss of oxidase activity is demonstrated in 2 hr incubations of the SMP with 10-100 microM DX in air-equilibrated medium with excess NADH to support redox-cycling of the drug. This oxidative mechanism for oxidase inactivation occurs in connection with a peroxidation process in the bulk membrane lipid, and is independent on turnover of the enzyme. It is related in a complex manner to the electron flux in the respiratory chain with antioxidant properties, and is maximal at the high reduction level of respiratory chain Complex I obtained in the presence of rotenone. Reduction of DX per se plays a minor role, and trace concentrations of chelatable metal ions (iron) are required to catalyse the reaction. Iron in the iron storage protein ferritin is released by DX, and at physiological low O2 concentrations ([O2] less than 20 microM), this iron is a better promoter of oxidase inactivation than is endogenous iron in the SMP. Kinetic analysis of inactivation data indicates the interaction of DX with low affinity (Km 35-55 microM) binding sites in the SMP membranes. Overall, the results point to the possible role of ferritin-iron in the mechanism of DX mitochondrial toxicity and argue against site specific effects of the DX-reduction/oxidation cycle on the cytochrome c oxidase or on its essential phospholipid (cardiolipin) environment.
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PMID:Inactivation of cytochrome c oxidase activity in mitochondrial membranes during redox cycling of doxorubicin. 184 35

NADH-lipoamide dehydrogenase mobilized iron from ferritin under aerobic conditions. Superoxide dismutase strongly inhibited this mobilization, indicating that the superoxide radical is generated by the enzymatic reaction and release iron from ferritin. Addition of lipoamide as an electron acceptor to NADH-lipoamide dehydrogenase increased the release of iron from ferritin and this release was partially inhibited by superoxide dismutase. Similarly, addition of menadione (2-methyl-1, 4-naphthoquinone) as an electron acceptor to xanthine-xanthine oxidase promoted the release of iron from ferritin and this release was strongly inhibited by superoxide dismutase. These results suggest that dihydrolipoamide and semiquinone of menadione can react with oxygen to form the superoxide radical that mediates release of iron from ferritin.
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PMID:Superoxide-mediated release of iron from ferritin by some flavoenzymes. 215 90

Oxidation of NADH has been observed in an in vitro system requiring NADH, vanadate, ascorbate, and phosphate. Similar results were observed with NADPH. Ascorbate provides the reducing equivalents necessary to reduce vanadate to vanadyl. Vanadyl autoxidizes producing superoxide which initiates a free radical chain reaction resulting in oxidation of NADH. Oxidation is inhibited by superoxide dismutase but not by catalase or ethanol. Ascorbate functions to initiate the free radical chain reaction but is not required in stoichiometric concentrations. At higher concentrations, ascorbate inhibits NADH oxidation. Inorganic phosphate was required for NADH oxidation. Dialysis of phosphate buffers against solutions containing apoferritin or conalbumin or addition of transition metal cations or chelators to the reaction medium did not alter dependence on phosphate. Phosphate and vanadate were interchangeable in their effects on kinetic parameters of NADH oxidation except that vanadate was 100 times more potent than phosphate. Vanadate participates directly in the initiating and propagating redox reactions of NADH oxidation. Phosphate may be important in lowering the energy of activation for the necessary transfer of hydronium ion and water in the transition state between vanadate anion and vanadyl cation.
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PMID:Vanadate-mediated oxidation of NADH: description of an in vitro system requiring ascorbate and phosphate. 273 68

Considerable evidence suggests that the release of iron from ferritin is a reductive process. A role in this process has been proposed for two hepatic enzymes, namely xanthine oxidoreductase and an NADH oxidoreductase. The abilities of xanthine and NADH to serve as a source of reducing power for the enzyme-mediated release of ferritin iron (ferrireductase activity) were compared with turkey liver and rat liver homogenates. The maximal velocity (Vmax.) for the reaction with NADH was 50 times greater than with xanthine; however, the substrate concentration required to achieve half-maximal velocity (Km) was 1000 times less with xanthine than with NADH. NADPH could be substituted for NADH with little loss in activity. Dicoumarol did not inhibit the reaction with NADH or NADPH, demonstrating that the ferrireductase activity with those substrates was not the result of the liver enzyme 'DT-diaphorase' [NAD(P)H dehydrogenase (quinone)]. A flavin nucleotide was required for ferrireductase activity with rat and turkey liver cytosol when xanthine, NADH or NADPH was used as the reducing substrate. FMN yielded twice the activity with NADH or NADPH, whereas FAD was twice as effective with xanthine as substrate. Kinetic comparisons, differences in lability and partial chromatographic resolution of the ferrireductase activities with the two types of reducing substrates strongly indicate that the ferrireductase activities with xanthine and NADH are catalysed by separate enzyme systems contained in liver cytosol. Complete inhibition by allopurinol of the ferrireductase activity endogenous to undialysed liver cytosol preparations and the ability of xanthine to restore equivalent activity to dialysed preparations indicate that the source of reducing power for the endogenous activity is xanthine. These studies suggest that xanthine, NADH or NADPH can serve as a source of reducing power for the enzyme-mediated reduction of ferritin iron, with a flavin nucleotide serving as the shuttle of electrons from the enzymes to the ferritin iron.
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PMID:The mobilization of ferritin iron by liver cytosol. A comparison of xanthine and NADH as reducing substrates. 277 99


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