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

Cytosolic and lysosomal ferritin and haemosiderin were isolated from rat livers which had been iron-loaded by four intraperitoneal injections of iron-dextran. The cytosolic and lysosomal ferritins, prepared in a phosphate-free medium, were subjected to gel-filtration chromatography on Sepharose 6B, yielding four fractions: a cytosolic monomeric (CMF) and void-volume ferritin fraction (CVVF), and a lysosomal monomeric (LMF) and void-volume ferritin fraction (LVVF). Of each fraction the following aspects were examined: (a) immunoreactivity against specific antiserum; (b) the Fe/P mass ratio and the effect of dialysis on this ratio using electron probe micro-analysis (EPMA); (c) morphology and Fe-specific imaging using electron spectroscopic imaging (ESI) and electron energy loss spectroscopy (EELS). For haemosiderin one aspect, the Fe/P ratio, was determined before and after extensive purification. The following results were obtained (a) All ferritin fractions reacted with anti- (rat liver ferritin). (b) The Fe/P ratios as determined in CMF in an haemosiderin were not affected by dialysis or extensive purification, respectively. The Fe/P ratio in CVVF was affected by dialysis. In the lysosomal fractions, only a trace of phosphorus (LVVF) or no phosphorus (LMF) was detected. (c) Morphologically, CMF and CVVF were found to be rather homogeneous; the iron core diameters of both fractions were in the known size range.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Lysosomal and cytosolic ferritins. A biochemical and electron-spectroscopic study. 264 18

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

Iron release from both human and horse spleen haemosiderin to desferrioxamine was substantially less than that released from ferritin samples. This finding contradicts a previous report [Kontoghiorges, Chambers & Hoffbrand (1987) Biochem. J. 241, 87-92]. Differences in phosphate content of cores and in core size between haemosiderin and ferritin did not account for the different iron-release rates. Iron released to acetate was found to stimulate lipid peroxidation in liposomes, whereas that released to stronger chelators such as citrate and desferal did not. Absorption spectra and gel-filtration studies suggest that the acetate-solubilized iron was in the form of low-molecular-mass (less than 5 kDa) ferrihydrite fragments.
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PMID:Iron release from haemosiderin and ferritin by therapeutic and physiological chelators. 276 11

Striopallidodentate calcinosis (Fahr's disease) is characterized clinically by seizures, rigidity, and dementia and pathologically by mineral deposition in the basal ganglia, dentate nucleus, and cerebral cortex. Disorders of iron and calcium-phosphate metabolism are thought to play a role in its pathogenesis. We present the case of a patient with familial striopallidodentate calcinosis who had porphyria cutanea tarda, refractory anemia, and pseudohypoparathyroidism type 2. The serum level of ferritin was markedly increased, serum iron and iron-binding capacity were below normal, and at autopsy she had deposition of iron in liver, spleen, bone marrow, and brain. She showed intermittent mild hypocalcemia, increased serum values of parathyroid hormone, elevated renal tubular reabsorption of phosphate, and low serum levels of 1,25-dihydroxyvitamin D, suggesting blunted renal responsiveness to endogenous parathyroid hormone. Pseudohypoparathyroidism type 2 was confirmed by infusion of synthetic parathyroid hormone, which gave a normal urinary cyclic adenosine monophosphate response, but a blunted phosphaturic response. After splenectomy for hypersplenism and weekly phlebotomies, she showed progressive improvement in function, mental status, weight, and seizure control. The hypothesis advanced is that the underlying pathophysiology of the separate diseases contributed to the formation of the brain stones through mechanisms of defective iron transport and free radical production.
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PMID:Abnormal systemic metabolism of iron, porphyrin, and calcium in Fahr's syndrome. 281 30

Sera from cancer patients specifically suppressed phosphofructokinase (fructose-6-phosphate kinase [PFK], EC 2.7.1.11), a rate-limiting enzyme in the glycolysis pathway. Among 418 cancerous sera, 68.7% evidence suppression; there was no organ specificity. Among 42 sera from early gastric cancer patients, 29 (69.0%) were positive, as were advanced gastric cancer, 14/19 (73.3%) pancreas cancer, and 75/101 (74.3%) lung cancer sera. In contrast 6/50 (12.0%) sera from patients with gastroduodenal ulcer, 3/23 (13.0%) with myoma uteri, and 0/6 with lung tuberculosis were positive. Patients with diabetes mellitus and those receiving steroid hormone therapy showed strong positive suppression. Comparative studies using other tumor markers (immunosuppressive acid protein, carcinoembryonic antigen, alpha-fetoprotein, beta 2-microglobulin, and ferritin) and the same sera used from PFK assay showed that the PFK method was two to three times more sensitive. Sephadex G-200 column chromatography revealed that the PFK-suppressive activity was retained in the postalbumin fraction. The PFK method may represent a promising new cancer screening method.
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PMID:A new cancer marker: a possible cancer screening method based on the suppression of phosphofructokinase by sera from cancer patients. 293 46

Our earlier studies showed that rabbit muscle phosphoglucomutase was irreversibly inactivated by exposure to a mixture of vitamin C, FeCl3 and O2. The enzyme lost about 70% of its phosphate (V.V. Desphande and J.G. Joshi, J. Biol. Chem. 260, 754-764, 1985). The present report shows that several other iron proteins can substitute for FeCl3 to a varying degree. The rate of inactivation by FeCl3 greater than ferritin greater than hemoglobin = hemerythrin greater than transferrin = ferridoxin = vitamin C. These iron compounds also produced dephosphoenzyme but did not dephosphorylate ATP, ADP, AMP or phospholipids.
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PMID:Differential loss of enzyme activity by vitC and iron containing proteins. 295 84

Polynuclear iron complexes of Fe(III) and phosphate occur in seawater and soils and in cells where the iron core of ferritin, the iron storage protein, contains up to 4500 Fe atoms in a complex with an average composition of (FeO.OH)8FeO.OPO3H2. Although phosphate influences the size of the ferritin core and thus the availability of stored iron, little is known about the nature of the Fe(III)-phosphate interaction. In the present study, Fe-phosphate interactions were analyzed in stable complexes of Fe(III).ATP which, in the polynuclear iron form, had phosphate at interior sites. Such Fe(III).ATP complexes are important not only as models but also because they may play a role in intracellular iron transport and in iron toxicity; the complexes were studied by extended x-ray absorption fine structure, EPR, NMR spectroscopy, and measurement of proton release. Mononuclear iron complexes exhibiting a g' = 4.3 EPR signal were formed at Fe:ATP ratios less than or equal to 1:3, and polynuclear iron complexes (Fe greater than or equal to 250, EPR silent at g' = 4.3) were formed at an Fe:ATP ratio of 4:1. No NMR signals due to ATP were observed when Fe was in excess (Fe:ATP = 4:1). Extended x-ray absorption fine structure analysis of the polynuclear Fe(III).ATP complex was able to distinguish an Fe-P distance at 3.27 A in addition to the octahedral O at 1.95 A and 4-5 Fe atoms at 3.36 A. The Fe-O and Fe-Fe distances are the same as in ferritin, and the Fe-P distance is analogous to that in another metal-ATP complex. An observable Fe-P environment in such a large polynuclear iron cluster as the Fe(III).ATP (4:1) complex indicates that the phosphate is distributed throughout rather than merely on the surface, in contrast to earlier models of chelate-stabilized iron clusters. Complexes of Fe(III) and ATP similar to those described here may form in vivo either as normal components of intracellular iron metabolism or during iron excess where the consequent alteration of free nucleotide triphosphate pools could contribute to the observed toxicity of iron.
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PMID:Fe(III).ATP complexes. Models for ferritin and other polynuclear iron complexes with phosphate. 298 69

The influence of various low molecular weight compounds on the transfer of 67Ga from human lactoferrin (LF) to horse spleen ferritin (HoFE) has been examined in vitro. When LF*67Ga complex was placed in competition with HoFE using a dialysis system the initial transfer rate (TR) of 67Ga to HoFE was slow and continuous. In the presence of 1 mM pyrophosphate (PPi) ascorbate and adenosine triphosphate (ATP), the TR was dramatically enhanced. This effect was concentration sensitive since reduction of the ATP to 0.1 mM eliminated the enhancement. Other intracellular compounds did not significantly influence the TR. Although PPi and ascorbate ions yielded larger TR's, ATP was more effective in the promotion of 67Ga transfer to HoFE. When the LF/HoFE concentration ratio was decreased, in the presence of ATP, the transfer of 67Ga was significantly increased. These results suggest that ferritin present intracellularly could remove and retain 67Ga entering the cell in the form of a LF*67Ga complex. Moreover, increased synthesis of ferritin and cytosolic phosphate compounds would appear to enhance this process.
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PMID:Compounds which mediate gallium-67 transfer from lactoferrin to ferritin. 299 49

Dietary supplementation with high-carbohydrate, guar gum fiber (HCF) is effective in acutely blunting postprandial blood glucose levels. We report the effect of such supplementation on the diet and nutritional status of a group of 16 subjects with non-insulin-dependent diabetes mellitus (NIDDM) who incorporated either HCF bars (35.7 g carbohydrate and 6.6 g guar gum/bar) or placebo bars (identical except for the absence of guar gum) into the diet for 6 mo as part of a double-blind, randomized clinical trial. The HCF subjects achieved mean daily intake of 4.8 +/- 0.4 bars, constituting 51.2 +/- 3.1% of total calories and providing 29.7 +/- 2.6 g guar gum daily. Energy intakes and body weight did not change significantly in either group. Food consumption patterns and nutrient intakes did change, although not enough to impair the nutritional integrity of the diet because the bars themselves served as a source of nutrients. The bars were rich in thiamin, B6, folacin, phosphorus, iron, zinc, and copper, adequately replacing any decrease in nutrient intake as a result of foods being dropped from the diet. In fact, daily intakes of B6, folacin, and copper actually increased due to contributions from the bars. Nutrients in which the bars were poor (vitamins A, C and B12) resulted in suboptimal intakes (less than 66% RDA). Although no significant change in nutritional status of the HCF group occurred as determined by arm muscle area, arm fat area, hemoglobin, hematocrit, or serum albumin, transferrin, iron, ferritin, calcium, phosphate, B12, and magnesium levels, these indicators of nutritional status are rather insensitive.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Nutritional risk of high-carbohydrate, guar gum dietary supplementation in non-insulin-dependent diabetes mellitus. 302 7

Female blood donors with low hematocrit levels detected by copper sulfate screening were selected randomly to receive either 75 mg of iron per day, as ferrous gluconate, or a calcium phosphate placebo. Their ferritin, serum iron, total iron-binding capacity, zinc protoporphyrin, and hemoglobin values, as well as their suitability to donate blood, were determined initially (Visit 1) and at four follow-up visits (Visits 2-5). By the second visit, the serum ferritin and iron values of donors receiving iron supplementation differed significantly from those of donors receiving placebo. By the fifth visit, a less marked but significant increase in hemoglobin had occurred in the iron group, but not in the placebo group. At no time was there a significant difference between the groups' suitability to donate blood, with each group donating at almost half of their visits. The authors conclude that iron supplementation at this dose level in deferred female blood donors improves their iron status and hemoglobin levels, but does not significantly increase their suitability to donate blood as compared with the suitability of placebo-treated donors.
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PMID:Iron supplementation in female blood donors deferred by copper sulfate screening. 304 20


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