Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: DrugBank:APRD00631 (Gel)
 14,881 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

An improved procedure was developed to extract prolyl hydroxylase from tendon cells of chick embryos with detergent, and improved assays were developed for both the activity of the enzyme and the amount of enzyme protein. Freshly isolated tendon cells were found to contain approx. 100 mug of enzyme protein per 10(8) cells and 40-50% of the enzyme protein was active. When the cells were cultured, they were found to contain the same amount of enzyme protein but only 15-20% of the enzyme protein was active. Gel filtration of cell extracts indicated that the active form of prolyl hydroxylase in freshly isolated tendon cells and incultured tendon cells had the same apparent size and the same activity per mug of immunoreactive protein as enzyme which was shown to be a tetramer. The inactive form was found to have about the same apparent size as subunits of the enzyme. When freshly isolated cells were incubated for 2 h in the presence of 40 mug per ml of ascorbate, there was a slight increase in the rate of hydroxyproline synthesis. In cultured cells, ascorbate at a concentration of 40 mug per ml caused a 2-fold increase in the rate of hydroxyproline synthesis within 30 min. However, ascorbate did not icrease the activity of prolyl hydroxylase in extracts from either cell system. Therefore it appears that the influence of ascorbate on synthesis of procollagen hydroxyproline by the cells studied here must be ascribed to a cofactor effect on the hydroxylation reaction similar to that observed with purified enzyme, and it does not involve "activation" of inactive enzyme protein to active enzyme as has been observed in cultures of L-929 and 3T6 mouse fibroblasts.
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PMID:Ascorbate increases the synthesis of procollagen hydroxyproline by cultured fibroblasts from chick embryo tendons without activation of prolyl hydroxyla. 17 37

A new soluble hemoprotein, designated as H-450, has been purified from pig liver. The absolute absorption spectrum of H-450 shows maxima at 550 and 428 nm. The dithionite-reduced H-450 has absorption peaks at 572, 540, and 450 nm; the unique Soret band at 450 nm is the basis for our tentative designation of this new hemoprotein as H-450 (hemoprotein 450). The spectrum of dithionite-reduced H-450 at 77 K gives two alpha peaks (571 and 566 nm), three beta peaks (546, 537, and 529 nm), and a Soret band at 449 nm. The prosthetic group of H-450 has been identified as protoheme IX. Gel electrophoresis experiments show that H-450 is composed of two nonidentical subunits, alpha and beta (mol wts = 61 000 and 45 000). H-450 contains 1 mol of heme/alphabeta dimer of 106 000 molecular weight. Preliminary sedimentation equilibrium experiments suggest a minimum molecular weight of 218 000 for the native protein. This corresponds to a tetramer, alpha2beta2 containing two heme groups. H-450 is not reduced by reduced nicotinamide adenine dinucleotide (NADH), NADH phosphate, ascorbate, or ferrocyanide. Neither reduced nor oxidized H-450 binds CO, 1 mM cyahide, or 1 mM azide. Dithionite-reduced H-450 is autoxidizable. The molar extinction coefficient of native H-450 is 261 X 103 at 280 nm and 263 X 103 at 428 nm. The purification procedure involves homogenization, high-speed centrifugation, ammonium sulfate fractionation, diethylaminoethylcellulose chromatography, density gradient centrifugation, a calcium phosphate gel step, and a second density gradient centrifugation. The procedure yeilds approximately 2 mg of purified protein from 750 g of pig liver.
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PMID:Isolation and properties of a new, soluble, hemoprotein (H-450) from pig liver. 99 Feb 54

The trabecular meshwork, a specialized tissue in the anterior chamber of the eye, plays a major role in the regulation of aqueous humor outflow. We studied the effects of ascorbic acid, a significant component in the aqueous humor, on gene expression of type I collagen in cultures of bovine trabecular meshwork cells. These cells were plated for 6 days, exposed to ascorbic acid in concentrations of 100, 250 and 500 micrograms/ml for 3 days and labeled with (3H)proline for the last 24 hrs. Cultures that did not receive ascorbic acid served as controls. Bacterial collagenase assays showed enhanced incorporation of (3H)proline into collagenous proteins in cultures treated with 100 and 250 micrograms/ml of ascorbic acid. Gel electrophoresis and fluorography revealed that ascorbic acid caused a 2.6- to 4.9-fold increase in production of alpha 1 (I) and alpha 2(I) collagen chains by trabecular meshwork cells. Such an increase was found, using a cDNA probe specific for pro alpha 1(I) chains, to be accompanied by an increase in steady-state mRNA levels. Similar findings were also yielded from in situ hybridization experiments. These results, coupled with previously demonstrated ascorbate-induced effects on glycosaminoglycan, fibronectin and laminin synthesis, suggest that ascorbic acid is a key mediator of the extracellular matrix production by trabecular meshwork cells. Fluctuations in its concentration may lead to alterations in the makeup and assembly of matrices underlying the cells.
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PMID:Ascorbic acid modulates collagen type I gene expression by cells from an eye tissue--trabecular meshwork. 130 7

The capacity of rat liver cytosol to decrease Fe/ADP ascorbate-induced lipid peroxidation in microsomes was evaluated using the chemiluminescence technique and measuring the formation of thiobarbituric acid-reactive substances (TBARS). The inhibiting effect of dialysed cytosol depended on the ascorbate concentration and was highest in the range of 1.0mM. Precipitation of cytosolic proteins with ammonium sulfate at 53% saturation yielded an active antioxidative fraction. Gel-filtration on Sephadex G-200 led to the separation of at least two cytosolic compounds of approximate molecular masses of 60 kDa and > 400 kDa. Both factors were active at 1.0mM ascorbate in the presence of freshly prepared microsomes. No inhibition of lipid peroxidation was observed using microsomes stored for one month at -70 degrees C.
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PMID:Ascorbate-dependent capacity of dialysed rat liver cytosol to prevent nonenzymatic lipid peroxidation. 147 60

1. The effect of normal rat liver cytosol on the level of Fe/ADP-ascorbate-induced lipid peroxidation in the total particulate fraction (mitochondria plus microsomes) has been studied. The intensity of lipid peroxidation was measured using chemiluminescence technique and malondialdehyde (MDA) formation. 2. Dialysed cytosol significantly decreased the level of chemiluminescence, and to a much lesser extent, the rate of MDA production. 3. Gel filtration on a Sephadex G-200 column led to appearance of at least three cytosolic fractions which suppressed the low-level chemiluminescence. 4. The discovered components differed from each other by their molecular masses, kinetics of chemiluminescence inhibition and effects on intensity of MDA formation. 5. The putative functional role of antioxidative defence factors from rat liver cytosol is discussed.
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PMID:On the role of rat liver cytosol in suppression of low-level chemiluminescence during nonenzymatic lipid peroxidation. 151 39

We have previously reported that scorbutic and fasted guinea pig sera contain an insulin-like growth factor-I (IGF-I)-reversible inhibitor of collagen, proteoglycan, and DNA synthesis in cultured cells. Here we report that IGF-binding protein (IGFBP) activity is increased in serum containing the inhibitor [125I]IGF-I or -II bound to these sera was eluted in the 30- to 50-kDa region of an S200 gel column. [125I]IGF-I affinity cross-linking analysis revealed that a 38-kDa cross-linked species increased markedly in fasted and scorbutic sera, with a lesser increase in a 34-kDa species, while scorbutic sera also yielded a 44-kDa species. Gel filtration of unlabeled sera showed a 10-fold increase in the activity of two proteins in the 30- to 50-kDa region from the experimental sera. Their activity correlated with their ability to inhibit binding of [125I]IGF-I to its cellular receptor, suggesting that they have the potential to inhibit IGF-I-dependent functions. Ligand blotting showed that 29 and 35-kDa IGFBPs were almost undetectable in normal serum, but were dramatically induced by scurvy and fasting, so that they accounted for close to 40% of the total circulating BPs. Total IGFBP-3 in the experimental sera was increased about 30%, while there was little effect of scurvy or fasting on the level of BP-3 activity isolated by acid extraction of the high mol wt region of the S200 column. An IGF-I analog with normal affinity for the 30- to 50-kDa BPs from fasted and scorbutic sera, but with reduced affinity for the cell receptor, was equivalent to IGF-I in reversing the inhibition of collagen synthesis by scorbutic guinea pig serum in human fibroblasts. Thus, reversal of inhibition appears to require initial saturation of IGFBPs. The overall results suggest that two circulating IGFBPs with unoccupied binding sites are induced in vitamin C-deficient or fasted guinea pigs and may be responsible for inhibition of IGF-I-dependent functions by sera from these animals.
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PMID:Elevated activity of low molecular weight insulin-like growth factor-binding proteins in sera of vitamin C-deficient and fasted guinea pigs. 170 59

Treatment of porcine heparin with the ferrous-EDTA complex and ascorbic acid for 24 h at 37 degrees C results in the degradation of most of the glycosaminoglycan to smaller fragments. About 65% of the products comprise oligosaccharides composed of less than 30 sugar units. The extent of depolymerization is decreased significantly if ascorbate or EDTA is not included in the reaction mixture. Gel filtration of the reaction products yielded fractions with narrow chain length ranges. The sulfate content of the fractions and their electrophoretic mobilities on cellulose acetate indicate that the components have equivalent charge densities. Depolymerization products with 20 or more sugar units retain significant anticoagulant potencies as measured by their effect in accelerating the neutralization of factor Xa by antithrombin.
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PMID:Depolymerization of heparin by complexed ferrous ions. 173 39

The effect of normal rat liver cytosol on the level of Fe/ADP-ascorbate-induced lipid peroxidation in the total particulate fraction (mitochondria plus microsomes) has been studied. The intensity of lipid peroxidation was measured using the chemiluminescence technique and by malonic dialdehyde (MDA) production. Dialyzed cytosol significantly decreased the level of chemiluminescence and, to a much lesser extent, the rate of MDA production. Gel filtration on a Sephadex G-200 column led to the appearance of at least three cytosolic fractions which suppressed the low-level chemiluminescence. These fractions differed from one another by their molecular masses, kinetics of chemiluminescence inhibition and effects on the intensity of MDA production. The putative functional role of antioxidative defence factors from rat liver cytosol is discussed.
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PMID:[Factors in rat liver cytosol, inhibiting chemiluminescence during nonenzymatic lipid peroxidation]. 174 22

Intestinal iron absorption is thought to proceed with iron mainly in the ferrous form, yet the novel iron complex, ferric maltol is an effective oral preparation. Although possessing a high oil: water partition coefficient, ferric maltol does not diffuse across the intestine but donates its iron to the endogenous uptake system. Reduction of the ferric iron in the gut lumen appears to precede iron uptake both from ferric maltol and from ferric nitrilotriacetic acid (NTA) which is a non-penetrating iron ligand. Uptake of radiolabelled iron (59Fe) into isolated fragments of rat small intestine was inhibited by the ferrous chelator, bathophenanthroline sulphonate (BPS) and enhanced at low concentrations by the reducing agent ascorbic acid. Spectrophotometric evidence was obtained that ferrous ions are generated from these ferric complexes in the presence of ascorbic acid and other reducing agents. The rate of ferrous ion formation was independent of ferric maltol concentration at low ascorbic acid levels and decreased with increasing ferric maltol concentration at higher levels of ascorbate. Maltol has a high affinity for ferric ions and may delay reduction at higher concentrations. By contrast, a higher rate of ferrous ion generation was seen with ferric NTA and this increased with iron ligand concentration. Washings from the intestinal lumen also brought about ferrous ion formation from these ferric ligands. Gel filtration revealed these reducing factors to be of low molecular weight. The washings, however, interfered with 59Fe uptake into the isolated fragments, but when reducing fractions only from the filtered washings were used, enhanced iron uptake was seen.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:The importance of reductive mechanisms for intestinal uptake of iron from ferric maltol and ferric nitrilotriacetic acid (NTA). 197 98

1. 59Fe absorption from the novel iron compound, ferric maltol, was studied in rats pretreated twice daily for two weeks with non-radioactive ferric maltol in oral doses containing 7 mg elemental iron. Tissue accumulation of 59Fe 2 h after administration of radioactive ferric maltol into the stomach was significantly lower in iron pretreated animals than in saline-treated controls. 2. 59Fe uptake from ferric maltol into isolated fragments of ileum and of duodenum was of similar magnitude in control animals but in iron-treated animals, duodenal uptake was significantly lower than that of the ileum. 3. Absorption of 59Fe was also investigated in anaesthetized rats after intestinal perfusion with saline (controls) or with 5 mM chenodeoxycholate to render the intestines more permeable. 4. Changes in permeability of the small intestine were monitored by estimating the amount of [14C]-mannitol absorbed and fluid secreted with reference to the non-absorbable [3H]-inulin in the perfusate effluents. 5. Despite the increased permeability of the intestines after bile salt treatment, there was little difference from control in the tissue accumulation of 59Fe from ferric maltol 2 h after intraduodenal administration. However 59Fe absorption from ferrous sulphate was significantly increased after bile salt treatment. 6. Gel filtration profiles of plasma made 5 and 60 min after intraduodenal administration of [59Fe]-ferric [3H]-maltol demonstrated that metal and ligand do not enter the circulation as the complex even when intestinal permeability is increased. 7. Uptake of 59Fe was investigated in isolated fragments of rat small intestine after saline or bile salt perfusion. Although 59Fe uptake from ferric maltol was somewhat greater in the bile salt-treated intestinal fragments, saturable kinetics were still observed. By contrast, "Fe uptake from ferrous sulphate: ascorbate was greatly enhanced by bile salt pretreatment and a very large diffusional component of uptake was evident. 8. It is concluded that iron uptake from ferric maltol may well be under endogenous regulatory control even in damaged intestines, so it is unlikely that this novel iron compound can bring about iron overload when administered orally.
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PMID:Evidence for regulatory control of iron uptake from ferric maltol across the small intestine of the rat. 201 22


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