Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.2.1.31 (beta-glucuronidase)
7,680 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

In these experiments, we assessed the role of hepatocyte lysosomes in biliary excretion of iron. We loaded rats with iron by feeding 2% carbonyl iron and collected bile for 24 h via bile fistulae from iron-loaded and control rats. In additional rats, bile was collected before and after the administration of colchicine. Rats were then killed and their livers were homogenized and fractionated for biochemical analyses or processed for electron microscopy and x-ray microanalysis. Inclusion of 2% carbonyl iron in the diet caused a 45-fold increase (P less than 0.001) in hepatic iron concentration compared with controls (1,826 +/- 159 vs. 38 +/- 6.7 micrograms/g liver, mean +/- SE). Electron microscopy with quantitative morphometry and x-ray microanalysis showed that the excess iron was sequestered in an increased number of lysosomes concentrated in the pericanalicular region of the hepatocyte. Iron loading was also associated with a twofold increase in biliary iron excretion (4.06 +/- 0.3 vs. 1.75 +/- 0.1 micrograms/g liver/24 h; P less than 0.001). In contrast, the biliary outputs of three lysosomal enzymes were significantly lower (P less than 0.0005) in iron-loaded rats compared with controls (mean +/- SE) expressed as mU/24 h/g liver: N-acetyl-beta-glucosaminidase, 26.7 +/- 4.6 vs. 66.2 +/- 13.4; beta-glucuronidase, 10.1 +/- 1.3 vs. 53.2 +/- 17.9; beta-galactosidase, 8.9 +/- 1.0 vs. 15.4 +/- 2.3. In iron-loaded rats but not in controls, biliary iron excretion was coupled to the release into bile of each of the three lysosomal hydrolases as assessed by linear regression analysis (P less than 0.001). In contrast, no relationships were found between biliary iron excretion and the biliary outputs of a plasma membrane marker enzyme (alkaline phosphodiesterase I) or total protein. After administration of colchicine, there was a parallel increase in biliary excretion of iron and lysosomal enzymes in iron-loaded rats, but not controls. We interpret these data to indicate that, in the rat, biliary iron excretion from hepatocyte lysosomes is an important excretory route for excess hepatic iron.
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PMID:Biliary excretion of iron from hepatocyte lysosomes in the rat. A major excretory pathway in experimental iron overload. 394 62

Previous studies have documented decreased activities of certain enzymes and altered function in polymorphonuclear leukocytes (PMN) during iron deficiency. The present study was undertaken to determine if the enzymatic abnormalities could be correlated with morphologic or quantitative change in PMN granules. Ultrastructural examination of primary and secondary granules and assessment of the secondary granule components alkaline phosphatase and vicinal glycol-containing glycoconjugates was performed in rabbit bone marrow, peripheral blood, and peritoneal heterophils. In addition, biochemical quantifications of the secondary granule component alkaline phosphatase and the primary granule marker beta-glucuronidase were performed. The results confirmed that a marked, significant decrease in alkaline phosphatase occurs in iron-deficient animals; however, no biochemical decrease in beta-glucuronidase activity was observed. Ultrastructurally, PMN secondary granules of iron-deficient rabbits tended to be more numerous than in controls when examined with morphometric and glycoconjugate staining methods, but lacked staining in alkaline phosphatase preparations. These results demonstrate that iron-deficient rabbits produce normal to increased quantities of primary and secondary granules, despite a uniform deficiency of alkaline phosphatase, a secondary granule marker.
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PMID:Ultrastructural morphology and cytochemistry of iron-deficient polymorphonuclear leukocytes. 394 78

We have observed pigmented cytoplasmic granules, with the characteristic staining properties of lipofuscin (ceroid, "wear-and-tear") pigment, in newborn human liver. The pigment is found at the periphery of the lobule in hepatocytes and some bile ductular cells. It is acid-fast, PAS-positive after diastase digestion, slightly argyophilic and sudanophilic, and markedly Schmorl's- and peroxidase positive in paraffin sections. Difficult to see in sections stained with hematoxylin and eosin, the pigment can be detected in unstained sections. The granules also resemble lipofuscin found in adult tissues, in their ultra-structural and enzymatic properties. They are polymorphic, contain granular material of moderate and high electron opacity, and are delimited by a single membrane. Acid phosphatase and beta-glucuronidase activities are visualized in the newborn granules, identifying them as lysosomes. The granules also contain copper and, to a much lesser extent, iron. The accumulation of lipofuscin pigment in lysosomes in many tissues correlates well with aging, and this process has been interpreted as a reflection of cellular degeneration or wear-and-tear. However, the presence of lipofuscin granules as a constant component of neonatal liver suggests that they are not a measure of cellular senescence.
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PMID:Lipofuscin (aging) pigment granules of the newborn human liver. 418 73

Four proteins, which have been designated A, B, C and D, have been purified from human parotid saliva. These proteins are the major constituents of parotid saliva which migrate rapidly to the anode in polyacrylamide electrophoresis at pH9.5. Gel filtration and polyacrylamide electrophoresis were employed in the purification procedures. After purification all four preparations were tested for homogeneity by electrophoresis at pH2.8 and 9.5, by isoelectric focusing in the pH range 3-10, by immunodiffusion, and by sedimentation in the analytical ultracentrifuge. None of the proteins showed significant activity in assays for amylase, acid and alkaline phosphatase, protease, lysozyme, ribonuclease, peroxidase, beta-glucuronidase, beta-galactosidase, iron-binding activity and esterase. No cross-reactions were detected with antisera specific for lactoferrin and 15 serum proteins. All four proteins were rich in glutamic acid, proline and glycine and were lacking completely the sulphur-containing amino acids. Proteins A and C contained no threonine or tyrosine. Carbohydrate could be demonstrated only in protein A at a concentration of 4% of the total protein.
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PMID:Purification and partial characterization of four proteins from human parotid saliva. 500 93

Recently, some knowledge of metabolic pathways, rather than individual enzyme activities of M. leprae, is becoming available. Ultimately this may be useful in devising culture media for M. leprae. Knowledge restricted to individual reactions may be misleading. For instance, the detection of GlcNacase and beta-glucuronidase and the subcellular localization of hyaluronic acid led to attempts to cultivate M. leprae on hyaluronic-acid based medium. Subsequent investigations suggested that there was no pathway for the breakdown of hyaluronic acid in M. leprae. The biochemical pathways for breaking down glucose and glycerol seem to be complete, and thus similar to many bacteria, but there is an unusually high level of one enzyme, 6-phosphogluconate dehydrogenase (6PGDH). Although 6-phosphogluconate is oxidized by M. leprae, and this is an unusual activity, reflecting very high levels of 6PGDH, glycerol may be a preferable energy source (on the basis of rates of oxidation by suspensions) for M. leprae in attempts to cultivate the bacterium. The utilization of 6-phosphogluconate might be important for other aspects of M. leprae metabolism not yet investigated (e.g., pentose metabolism) or it may be an adaption, not needed in vitro, to its existence in host macrophages. Alternatively, its oxidation may be a way of rapidly generating NADPH at critical times for the bacterium. Other unusual activities which have been reported are the presence of an enzyme characteristic of chemoautotrophism , completely surprising in view of the biology of M. leprae. This report needs to be confirmed--some aspects, in fact, have failed to be confirmed. o-Diphenoloxidase activity is unique, among mycobacteria, to M. leprae, but there is still doubt over whether or not it is an enzymatic activity and its function is unknown. A transpeptidase which may be involved in cell wall synthesis, recently demonstrated in M. leprae, is a typical mycobacterial enzyme. It is now known that iron could be supplied to M. leprae in potential media in the form of ferriexochelin from M. neoaurum . Two "deletions" in the metabolic processes of M. leprae have been observed. Catalase appears to be absent in M. leprae; its addition to media stimulates the growth of some organisms since peroxides form in the bacteriological media . Purine synthesis de novo occurred at a very low rate compared with purine scavenging. Whether this is an adaption to growth in vivo is not known.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Metabolism in Mycobacterium leprae: its relation to other research on M. leprae and to aspects of metabolism in other mycobacteria and intracellular parasites. 614 38

The present study demonstrates for the first time that iron ions can induce lipid peroxidation in intact macrophages without causing cell death. Macrophage lipid peroxidation increases cell-mediated oxidation of LDL, enhances the release of interleukin 1 and inhibits the release of apolipoprotein E from the macrophages. When cultured macrophages were exposed to ferrous ions (50 microM FeSO4) for 4 h at 37 degrees C, cellular lipid peroxidation (measured by analyses of malondialdehyde (MDA), conjugated dienes (CD), and lipid peroxides (PD)) increased 2-4-fold in comparison with non-treated cells. This process was iron-dose dependent, reached its maximum after 4 h of incubation, and was accompanied by 68% and 53% reductions in the content of the cellular linoleic (18:2), and arachidonic acid (20:4), respectively, and by 29% and 36% reductions of cellular vitamin E and vitamin A, respectively. Cell viability (measured by trypan blue exclusion, by [3H]thymidine incorporation into DNA, by analysis of the release of lactate dehydrogenase (LDH) or [3H]adenine), and cell morphology (studied by scanning electron microscopy) were not significantly affected by the iron-induced oxidative stress. Manitol and dimethylthiourea (DMTU), but not catalase or superoxide dismutase (SOD), significantly inhibited iron-induced cellular lipid peroxide formation, suggesting that hydroxyl radical, but not superoxides or hydrogen peroxides, mediated the iron-induced cellular lipid peroxidation. Incubation of LDL (0.2 mg of protein/ml) with oxidized macrophages resulted in LDL lipids peroxidation, as evidenced by an 8-fold increase in the LDL associated MDA in comparison with LDL that was incubated under similar conditions with non-oxidized macrophages. Furthermore, oxidation of LDL by oxidized macrophages in the presence of copper ions (10 microM CuSO4) was 2-fold higher in comparison with oxidation of LDL by non-oxidized macrophages. The release of apolipoprotein E from oxidized macrophages decreased by 50%, whereas macrophage release of beta-glucuronidase and of interleukin-1 beta increased by 83% and by a factor of 6, respectively. This study demonstrates for the first time that iron ions induce oxidation of the cellular polyunsaturated fatty acids in intact macrophages and that this cellular lipid peroxidation can subsequently induce LDL oxidation.
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PMID:Iron induces lipid peroxidation in cultured macrophages, increases their ability to oxidatively modify LDL, and affects their secretory properties. 784 Aug 15

Sensitive and selective high performance liquid chromatographic (HPLC) methods for the quantification of 1,2-diethyl-3-hydroxypyridin-4-one (CP94), its iron complex [Fe(III) (CP94)3] and glucuronide metabolite (CP94-GLUC) in urine and serum of thalassaemic patients are described. Three separate analyses are involved. The first assay quantifies both CP94 and its iron complex. This procedure requires the conversion of the iron complex to the free ligand and is carried out using diethylenetriaminepentaacetic acid (DTPA). CP94 and the internal standard, 1-propyl-2-ethyl-3-hydroxypyridin-4-one (CP95) present in either serum or urine are then extracted at pH 7.0 with dichloromethane. Extraction efficiency is 96.0 +/- 5.6% and 100 +/- 7.1% for CP94 and CP95, respectively, and 31.2 +/- 2.1% at 30 microM and 53.2 +/- 4.2% at 300 microM for the corresponding iron complex. In the second assay, samples are incubated (16 h) with beta-glucuronidase and processed as before. In this assay, the drug, its iron complex and glucuronide conjugate are measured. In the third assay the iron complex of CP94, [Fe(III) (CP94)3] is quantified. From the three separate analyses it is possible to calculate the individual concentrations of the three separate components present in serum and urine of thalassaemic patients. Calibration for both components, i.e. CP94 (assays 1 and 2) and its iron complex (assay 3) are linear with correlation coefficients > 0.99 and are reproducible over the required concentration range of 0-500 microM for the free ligand and 0-100 microM for the iron complex. The minimum quantifiable level is 0.5 microM for the free ligand and 1.0 microM for the iron complex.
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PMID:HPLC determination of 1,2-diethyl-3-hydroxypyridin-4-one (CP94), its iron complex [Fe(III) (CP94)3] and glucuronide conjugate [CP94-GLUC] in serum and urine of thalassaemic patients. 798 22

The scavenging by procyanidines (polyphenol oligomers from Vitis vinifera seeds, CAS 85594-37-2) of reactive oxygen species (ROS) involved in the onset (HO degrees) and the maintenance of microvascular injury (lipid radicals R degrees, RO degrees, ROO degrees) has been studied in phosphatidylcholine liposomes (PCL), using two different models of free radical generation: a) iron-promoted and b) ultrasound-induced lipid peroxidation. In a) lipid peroxidation was assessed by determination of thiobarbituric acid-reactive substances (TBARS); in b) by determination of conjugated dienes, formation of breakdown carbonyl products (as 2,4-dinitrophenylhydrazones) and loss of native phosphatidylcholine. In the iron-promoted (Fenton-driven) model, procyanidines had a remarkable, dose-dependent antilipoperoxidant activity (IC50 = 2.5 mumol/l), more than one order of magnitude greater than that of the monomeric unit catechin (IC50 = 50 mumol/l), activity which is due, at least in part, to their metal-chelating properties. In the more specific model b), which discriminates between the initiator (hydroxyl radical from water sonolysis) and the propagator species of lipid peroxidation (the peroxyl radical, from autooxidation of C-centered radicals), procyanidines are highly effective in preventing conjugated diene formation in both the induction (IC50 = 0.1 mumol/l) and propagation (IC50 = 0.05 mumol/l) phases (the scavenging effect of alpha-tocopherol was weaker, with IC50 of 1.5 and 1.25 mumol/l). In addition, procyanidines at 0.5 mumol/l markedly delayed the onset of the breakdown phase (48 h), totally inhibiting during this time the formation of degradation products (the lag-time induced by alpha-tocopherol was only of 24 h at 10 mumol/l concentration). The HO degrees entrapping capacity of these compounds was further confirmed by UV studies and by electron spin resonance (ESR) spectroscopy, using DMPO as spin trapper: procyanidines markedly reduced, in a dose-dependent fashion, the signal intensity of the DMPO-OH radical spin adduct (100% inhibition at 40 mumol/l). The results of the second part of this study show that procyanidines, in addition to free radical scavenging action, strongly and non-competitively, inhibit xanthine oxidase activity, the enzyme which triggers the oxy radical cascade (IC50 = 2.4 mumol/l). In addition procyanidines non-competitively inhibit the activities of the proteolytic enzymes collagenase (IC50 = 38 mumol/l) and elastase (IC50 = 4.24 mumol/l) and of the glycosidases hyaluronidase and beta-glucuronidase (IC50 = 80 mumol/l and 1.1 mumol/l), involved in the turnover of the main structural components of the extravascular matrix collagen, elastin and hyaluronic acid.(ABSTRACT TRUNCATED AT 400 WORDS)
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PMID:Free radicals scavenging action and anti-enzyme activities of procyanidines from Vitis vinifera. A mechanism for their capillary protective action. 802 28

Administration of hepatotoxic doses of diquat to male Fischer-344 rats increases biliary excretion of nonheme iron, whereas comparably hepatotoxic doses of acetaminophen decrease biliary export of iron. The effects of acetaminophen and diquat on the activities in bile of representative lysosomal enzymes, beta-N-acetylglucosaminidase (beta-NAG) and beta-glucuronidase (beta-GLUC) were examined as a means of assessing the possible role of lysosomal exocytosis in the effects of these hepatotoxins on biliary excretion of iron. In pentobarbital-anesthetized male Fischer-344 rats, diquat at 0.1 mmol/kg increased the biliary export of biliary beta-NAG and beta-GLUC, in conjunction with similar increases in iron. Sprague-Dawley rats, which are resistant to diquat-induced hepatic necrosis despite showing marked oxidant stress responses, showed no increases in biliary efflux of iron, beta-NAG, or beta-GLUC in response to diquat. Conversely, acetaminophen at doses of 400 or 1500 mg/kg markedly decreased biliary concentrations and efflux rates of beta-NAG and beta-GLUC in Fischer-344 rats in parallel with decreases in biliary iron, suggesting that the hepatotoxin-induced effects on biliary iron excretion may be mediated through effects on lysosomal exocytosis. Both acetaminophen and diquat increased total protein content of bile in both strains of rats; however, the proteins excreted after administration of diquat to Fischer-344 rats showed marked increases in contents of protein carbonyls, as assayed with 2,4-dinitrophenylhydrazine, whereas biliary proteins in acetaminophen-treated animals were not more oxidized than in controls. Sprague-Dawley rats given diquat showed no increase in the biliary excretion of protein carbonyls, despite the increased excretion of glutathione disulfide observed in these animals. The significant increases in biliary excretion of protein carbonyls by the diquat-treated Fischer-344 rats suggest oxidation of cellular proteins catalyzed by chemically reactive iron chelates and the excretion of at least some of the oxidized proteins to the bile, possibly through lysosomal exocytosis. The effects of acetaminophen on biliary protein excretion do not appear to involve oxidation.
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PMID:Biliary excretion of lysosomal enzymes, iron, and oxidized protein in Fischer-344 and Sprague-Dawley rats and the effects of diquat and acetaminophen. 812 94

The guinea pig model of iron overload, described in the preceding article, was used to investigate the mechanism of excess iron toxicity in hepatic and cardiac tissues. Effects of iron overload on both lysosomal membrane fragility and membrane peroxidation were studied. The free activity of selected myocardial and hepatic lysosomal enzymes, in addition to serum activity, was measured in guinea pigs treated with iron dextran (0.25, 0.5, 1.0, and 2.0 g Fe/kg body weight); controls received dextran. Levels of malondialdehyde were also determined in whole homogenates of heart and liver in animals loaded with 0.5 and 1.5 g Fe/kg of iron dextran. Results indicated that the free activity of hepatic glucosaminidase (p < 0.05) and beta-glucuronidase (p < 0.05) were significantly elevated at all levels of iron loading; hepatic acid phosphatase was increased at all but the lowest iron dose. Similarly, increased serum glucosaminidase activity was observed (p < 0.01) at all dose levels. When compared to pooled controls, the free activity of myocardial glucosaminidase was also elevated (p < 0.05) at all levels of loading. However, myocardial acid phosphatase was increased only at the highest iron dose (p < 0.01). Increased malondialdehyde was measured at the high iron dose (1.5 g Fe/kg) in whole homogenates of both heart and liver (p < 0.01). We conclude that iron loading in this model profoundly alters the stability of hepatic and myocardial lysosomal membranes; furthermore, changes in serum glucosaminidase activity may be reflective of modified tissue lysosomal properties. Elevated levels of malondialdehyde in whole homogenates suggest that iron-mediated lipid peroxidation may be responsible in part for enhanced lysosomal membrane fragility.
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PMID:Iron-induced myocardial and hepatic lysosomal abnormalities in the guinea pig. 824 21


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