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51.
The specific activity of hepatic microsomal and peroxisomal 3-hydroxy-3-methylglutaryl coenzyme A reductase (HMG-CoA reductase) was determined at different times during a 24 hour cycle from cholestyramine treated rats. The microsomal HMG-CoA reductase activity displayed a peak at D-6 (6th hour of the dark cycle) as previously reported, whereas, the peroxisomal HMG-CoA reductase activity was the highest at L-2 (2nd hour of the light cycle). Immunoblots of the peroxisomal HMG-CoA reductase suggest that the increase in enzyme activity at L-2 is due to changes in enzyme mass. The different cyclic variations observed in microsomal and peroxisomal HMG-CoA reductase activity may suggest different mechanisms of regulation. 相似文献
52.
HANDE GURER-ORHAN HILMI ORHAN SIBEL SUZEN M. ORHAN PÜSKÜLLÜ ERDEM BUYUKBINGOL 《Journal of enzyme inhibition and medicinal chemistry》2013,28(2):241-247
New, except 1d, melatonin analogue benzimidazole derivatives were synthesized and characterized in the present study. The potential role of melatonin as an antioxidant by scavenging and detoxifying ROS raised the possibility that compounds that are analogous to melatonin can also be used for their antioxidant properties. Therefore the antioxidant effects of the newly synthesized compounds were investigated in vitro by means of their inhibitory effect on hydrogen peroxide-induced erythrocyte membrane lipid peroxidation (EMLP) and on various erythrocyte antioxidant enzymes viz. superoxide dismutase (SOD), catalase (CAT) and glucose-6-phosphate dehydrogenase (G6PD). The synthesized benzimidazole derivatives showed remarkable antioxidant activity in vitro in the H2O2-induced EMLP system. Furthermore their effects on various antioxidant enzymes are discussed and evaluated from the perspective of structure- activity relationships. 相似文献
53.
MAGDALENA WITEK PIOTR NOWICKI EWA B. ŚLIWIŃSKA PIOTR SKÓRKA JOSEF SETTELE KARSTEN SCHÖNROGGE MICHAL WOYCIECHOWSKI 《Ecological Entomology》2010,35(5):557-564
1. Phengaris butterflies are obligatory social parasites of Myrmica ants. Early research suggested that there is a different Myrmica host species for each of the five European Phengaris social parasites, but more recent studies have shown that this was an oversimplification. 2. The pattern of host ant specificity within a Phengaris teleius metapopulation from southern Poland is reported. A combination of studying the frequency distribution of Phengaris occurrence and morphometrics on adult butterflies were used to test whether use of different host species is reflected in larval development. 3. Phengaris teleius larvae were found to survive in colonies of four Myrmica species: M. scabrinodis, M. rubra, M. ruginodis, and M. rugulosa. Myrmica scabrinodis was the most abundant species under the host plant but the percentage of infested nests was similar to other host ant species at two sites and lower in comparison to nests of M. rubra and M. ruginodis at the other two sites. Morphometric measurements of adult butterflies reared by wild colonies of M. scabrinodis and M. ruginodis showed that wing size and number of wing spots were slightly greater for adults eclosing from nests of M. ruginodis. 4. Our results suggest that P. teleius in the populations studied is less specialised than previously suggested. The results are consistent with the hypothesis that P. teleius is expected to be the least specific of the European Phengaris species, as it has the largest and best defended fourth‐instar caterpillars and, as a predatory species, it spends less time in the central larval chambers of the host colonies. The fact that individuals reared by M. ruginodis had wider hind wings may suggest that P. teleius had better access to resources in M. ruginodis than in M. scabrinodis colonies. 相似文献
54.
Waliza Ansar Sumi Mukhopadhyay SK. Hasan Habib Shyamasree Basu Bibhuti Saha Asish Kumar Sen CN. Mandal Chitra Mandal 《Glycoconjugate journal》2009,26(9):1151-1169
Human C-reactive protein (CRP), as a mediator of innate immunity, removed damaged cells by activating the classical complement
pathway. Previous studies have successfully demonstrated that CRPs are differentially induced as glycosylated molecular variants
in certain pathological conditions. Affinity-purified CRPs from two most prevalent diseases in India viz. tuberculosis (TB) and visceral leishmaniasis (VL) have differential glycosylation in their sugar composition and linkages. As anemia is a common manifestation in TB and
VL, we assessed the contributory role of glycosylated CRPs to influence hemolysis via CRP-complement-pathway as compared to
healthy control subjects. Accordingly, the specific binding of glycosylated CRPs with erythrocytes was established by flow-cytometry
and ELISA. Significantly, deglycosylated CRPs showed a 7–8-fold reduced binding with erythrocytes confirming the role of glycosylated
moieties. Scatchard analysis revealed striking differences in the apparent binding constants (104–105 M−1) and number of binding sites (106–107sites/erythrocyte) for CRP on patients’ erythrocytes as compared to normal. Western blotting along with immunoprecipitation
analysis revealed the presence of distinct molecular determinants on TB and VL erythrocytes specific to disease-associated
CRP. Increased fragility, hydrophobicity and decreased rigidity of diseased-erythrocytes upon binding with glycosylated CRP
suggested membrane damage. Finally, the erythrocyte-CRP binding was shown to activate the CRP-complement-cascade causing hemolysis,
even at physiological concentration of CRP (10 μg/ml). Thus, it may be postulated that CRP have a protective role towards
the clearance of damaged-erythrocytes in these two diseases. 相似文献
55.
56.
3-Hydroxy-3-methylglutaryl coenzyme A reductase localization in rat liver peroxisomes and microsomes of control and cholestyramine-treated animals: quantitative biochemical and immunoelectron microscopical analyses 总被引:7,自引:2,他引:5 下载免费PDF全文
3-Hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase, a key regulatory enzyme involved in cholesterol biosynthesis, has recently been reported to be present in rat liver peroxisomes (Keller, G.A., M.C. Barton, D.J. Shapiro, and S.J. Singer, 1985, Proc. Natl. Acad. Sci. USA, 82:770-774). Immunoelectron labeling of ultrathin frozen sections of normal liver, using two monoclonal antibodies to purified rat liver microsomal HMG-CoA reductase, indicated that the enzyme is present in the matrix of peroxisomes. This study is a quantitative biochemical and immunoelectron microscopical analysis of HMG-CoA reductase in rat liver peroxisomes and microsomes of normal and cholestyramine-treated animals. Cholestyramine treatment produced a six- to sevenfold increase in the specific activity of peroxisomal HMG-CoA reductase, whereas the microsomal HMG-CoA reductase specific activity increased by about twofold. Using a computer program that calculates optimal linear combinations of marker enzymes, it was determined that between 20 and 30% of the total reductase activity was located in the peroxisomes of cholestyramine-treated animals. Less than 5% of the reductase activity was present in peroxisomes under control conditions. Quantitation of the immunoelectron microscopical data was in excellent agreement with the biochemical results. After cholestyramine treatment there was an eightfold increase in the density of gold particles per peroxisome, and we estimate about a threefold increase in the labeling of the ER. 相似文献
57.
Subcellular localization of sterol carrier protein-2 in rat hepatocytes: its primary localization to peroxisomes 总被引:9,自引:2,他引:7 下载免费PDF全文
G A Keller T J Scallen D Clarke P A Maher S K Krisans S J Singer 《The Journal of cell biology》1989,108(4):1353-1361
Sterol carrier protein-2 (SCP-2) is a nonenzymatic protein of 13.5 kD which has been shown in in vitro experiments to be required for several stages in cholesterol utilization and biosynthesis. The subcellular localization of SCP-2 has not been definitively established. Using affinity-purified rabbit polyclonal antibodies against electrophoretically pure SCP-2 from rat liver, we demonstrate by immunoelectron microscopic labeling of ultrathin frozen sections of rat liver that the largest concentration of SCP-2 is inside peroxisomes. In addition the immunolabeling indicates that there are significant concentrations of SCP-2 inside mitochondria, and associated with the endoplasmic reticulum and the cytosol, but not inside the Golgi apparatus, lysosomes, or the nucleus. These results were confirmed by immunoblotting experiments with proteins from purified subcellular fractions of the rat liver cells carried out with the anti-SCP-2 antibodies. The large concentration of SCP-2 inside peroxisomes strongly supports the proposal that peroxisomes are critical sites of cholesterol utilization and biosynthesis. The presence of SCP-2 inside peroxisomes and mitochondria raises questions about the mechanisms involved in the differential targeting of SCP-2 to these organelles. 相似文献
58.
Phosphomevalonate kinase catalyzes the conversion of mevalonate-5-phosphate to mevalonate-5-diphosphate and was originally believed to be a cytosolic enzyme. In this study we have localized the phosphomevalonate kinase gene to chromosome 1p13-1q22-23 and present a genomic map indicating that the gene spans more than 8.4 kb in the human genome. Furthermore, we show that message levels and enzyme activity of rat liver phosphomevalonate kinase are regulated in response to dietary sterol levels and that this regulation is coordinate with 3-hydroxy-3-methylglutaryl coenzyme A reductase, the rate-limiting enzyme of cholesterol biosynthesis. In addition, we demonstrate that phosphomevalonate kinase is a peroxisomal protein which requires the C-terminal peroxisomal targeting signal, Ser-Arg-Leu, for localization to the organelle. 相似文献
59.
60.
Kovacs WJ Tape KN Shackelford JE Duan X Kasumov T Kelleher JK Brunengraber H Krisans SK 《Histochemistry and cell biology》2007,127(3):273-290
Previous studies have indicated that the early steps in the isoprenoid/cholesterol biosynthetic pathway occur in peroxisomes.
However, the role of peroxisomes in cholesterol biosynthesis has recently been questioned in several reports concluding that
three of the peroxisomal cholesterol biosynthetic enzymes, namely mevalonate kinase, phosphomevalonate kinase, and mevalonate
diphosphate decarboxylase, do not localize to peroxisomes in human cells even though they contain consensus peroxisomal targeting
signals. We re-investigated the subcellular localization of the cholesterol biosynthetic enzymes of the pre-squalene segment
in human cells by using new stable isotopic techniques and data computations with isotopomer spectral analysis, in combination
with immunofluorescence and cell permeabilization techniques. Our present findings clearly show and confirm previous studies
that the pre-squalene segment of the cholesterol biosynthetic pathway is localized to peroxisomes. In addition, our data are
consistent with the hypothesis that acetyl-CoA derived from peroxisomal β-oxidation of very long-chain fatty acids and medium-chain
dicarboxylic acids is preferentially channeled to cholesterol synthesis inside the peroxisomes without mixing with the cytosolic
acetyl-CoA pool. 相似文献