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281.
Serotonin is a major neurotransmitter that controls many functions, ranging from mood and behaviour through to sleep and motor functions. The non-enzymatic oxidation of serotonin is of significant importance as some oxidation products are considered to be neurotoxic. An interaction between copper and serotonin has been suggested by symptoms observed in a number of neurodegenerative diseases such as Wilson's and Prion diseases. Using PC12 cells as a model of neuronal cells, we show that the interaction between copper and serotonin is toxic to undifferentiated cells. The toxicity is largely due to reactive oxygen species as cell death is significantly reduced in the presence of the antioxidant mannitol. Differentiation of the PC12 cells also confers resistance to the oxidative process. In vitro oxidation of serotonin by copper results in the eventual formation of a coloured pigment, thought to be a melanin-like polymeric species. Using spectroscopic methods we provide evidence for the formation of a single intermediate product. This dimeric intermediate was identified and characterized as 5,5'-dihydroxy-4,4'-bitryptamine. These results indicate that copper structurally alters serotonin and this process may play a role in copper related neurodegenerative diseases. 相似文献
282.
Disulfide reductases of host-colonising bacteria are involved in the expression of virulence factors, resistance to drugs,
and elimination of toxic compounds. Large-scale genome analyses of 281 prokaryotes identified CXXC and CXXC-derived motifs
in each microorganism. The total number of these motifs showed correlations with genome size and oxygen tolerance of the prokaryotes.
Specific bioinformatic analyses served to identify putative disulfide reductases in the Campylobacterales Campylobacter jejuni, Helicobacter pylori, Wolinella succinogenes and Arcobacter butzleri which colonise the gastrointestinal tract of higher animals. Three filters applied to the genomes of these species yielded
35, 25, 28 and 34 genes, respectively, encoding proteins with the characteristics of disulfide reductases. Ten proteins were
common to the four species, including four belonging to the thioredoxin system. The presence of thioredoxin reductase activities
was detected in the four bacterial species by observing dithiobis-2-nitrobenzoic acid reduction with β-nicotinamide adenine
dinucleotide phosphate as cofactor. Phylogenetic analyses of the thioredoxin reductases TrxB1 and TrxB2 of the four Campylobacterales were performed. Their TrxB1 proteins were more closely related to those of Firmicutes than to the corresponding proteins of other Proteobacteria. The
Campylobacterales TrxB2 proteins were closer to glutathione reductases of other organisms than to their respective TrxB1 proteins. The phylogenetic features of the Campylobacterales thioredoxin reductases suggested a special role for these enzymes
in the physiology of these bacteria.
Electronic Supplementary Material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
283.
Heart-type fatty acid-binding protein (H-FABP) is a major fatty acid-binding factor in skeletal muscles. Genetic lack of H-FABP
severely impairs the esterification and oxidation of exogenous fatty acids in soleus muscles isolated from chow-fed mice (CHOW-solei)
and high fat diet-fed mice (HFD-solei), and prevents the HFD-induced accumulation of muscle triacylglycerols (TAGs). Here,
we examined the impact of H-FABP deficiency on the relationship between fatty acid utilization and glucose oxidation. Glucose
oxidation was measured in isolated soleus muscles in the presence or absence of 1 mM palmitate (simple protocol) or in the
absence of fatty acid after preincubation with 1 mM palmitate (complex protocol). With the simple protocol, the mutation slightly
reduced glucose oxidation in CHOW-muscles, but markedly increased it in HFD-muscles; unexpectedly, this pattern was not altered
by the addition of palmitate, which reduced glucose oxidation in both CHOW- and HFD-solei irrespective of the mutation. In
the complex protocol, the mutation first inhibited the synthesis and accumulation of TAGs and then their mobilization; with
this protocol, the mutation increased glucose oxidation in both CHOW- and HFD-solei. We conclude: (i) H-FABP mediates a non-acute
inhibition of muscle glucose oxidation by fatty acids, likely by enabling both the accumulation and mobilization of a critical
mass of muscle TAGs; (ii) H-FABP does not mediate the acute inhibitory effect of extracellular fatty acids on muscle glucose
oxidation; (iii) H-FABP affects muscle glucose oxidation in opposing ways, with inhibition prevailing at high muscle TAG contents. 相似文献
284.
Onay-Besikci A 《Molecular and cellular biochemistry》2007,296(1-2):121-127
The goal of this study was to investigate the effect of 1 mM exogenous lactate on cardiac function, and some metabolic parameters,
such as glycolysis, glucose oxidation, lactate oxidation, and fatty acid oxidation, in isolated working rat hearts. Hearts
from male Sprague-Dawley rats were isolated and perfused with 5 mM glucose, 1.2 mM palmitate, and 100 μU/ml insulin with or
without 1 mM lactate. The rates of glycolysis, glucose, lactate, and fatty acid oxidation were determined by supplementing
the buffer with radiolabeled substrates. Cardiac function was similar between lactate+ and lactate− hearts. Glycolysis was
not affected by 1 mM lactate. The addition of lactate did not alter glucose oxidation rates. Interestingly, palmitate oxidation
rates almost doubled when 1 mM lactate was present in the perfusate. This study suggests that subst rate supply to the heart
is crucially important when evaluating the data from metabolic studies. 相似文献
285.
d'Andréa S Canonge M Beopoulos A Jolivet P Hartmann MA Miquel M Lepiniec L Chardot T 《Biochimie》2007,89(2):222-229
In a previous work, we presented evidence for the presence of a protein encoded by At5g50600 in oil bodies (OBs) from Arabidopsis thaliana [P. Jolivet, E. Roux, S. D'Andrea, M. Davanture, L. Negroni, M. Zivy, T. Chardot, Protein composition of oil bodies in Arabidopsis thaliana ecotype WS, Plant Physiol. Biochem. 42 (2004) 501-509]. Using specific antibodies and proteomic techniques, we presently confirm the existence of this protein, which is a member of the short-chain steroid dehydrogenase reductase superfamily. We have measured its activity toward various steroids (cholesterol, dehydroepiandrosterone, cortisol, corticosterone, estradiol, estrone) and NAD(P)(H), either within purified OBs or as a purified bacterially expressed chimera. Both enzymatic systems (OBs purified from A. thaliana seeds as well as the chimeric enzyme) exhibited hydroxysteroid dehydrogenase (HSD) activity toward estradiol (17beta-hydroxysteroid) with NAD+ or NADP+, NADP+ being the preferred cofactor. Low levels of activity were observed with cortisol or corticosterone (11beta-hydroxysteroids), but neither cholesterol nor DHEA (3beta-hydroxysteroids) were substrates, whatever the cofactor used. Similar activity profiles were found for both enzyme sources. Purified OBs were found to be also able to catalyze estrone reduction (17beta-ketosteroid reductase activity) with NADPH. The enzyme occurring in A. thaliana OBs can be classified as a NADP+-dependent 11beta-,17beta-hydroxysteroid dehydrogenase/17beta-ketosteroid reductase. This enzyme probably corresponds to AtHSD1, which is encoded by At5g50600. However, its physiological role and substrates still remain to be determined. 相似文献
286.
An unusual propionigenic bacterium was isolated from the intestinal tract of the soil-feeding termite Thoracotermes macrothorax. Strain TmPN3 is a motile, long rod that stains gram-positive, but reacts gram-negative in the KOH test. It forms terminal
endospores and ferments lactate, glucose, lactose, fructose, and pyruvate to propionate and acetate via the methyl-malonyl-CoA
pathway. Propionate and acetate are formed at a ratio of 2:1, typical of most propionigenic bacteria. Under a H2/CO2 atmosphere, the fermentation product pattern of glucose, fructose, and pyruvate shifts towards propionate formation at the
expense of acetate. Cell suspensions reduce oxygen with lactate, glucose, glycerol, or hydrogen as electron donor. In the
presence of oxygen, the product pattern of lactate fermentation shifts from propionate to acetate production. 16S rRNA gene
sequence analysis showed that strain TmPN3 is a firmicute that clusters among the Acidaminococcaceae, a subgroup of the Clostridiales
comprising obligately anaerobic, often endospore-forming bacteria that possess an outer membrane. Based on phenotypic differences
and less than 92% sequence similarity to the 16S rRNA gene sequence of its closest relative, the termite hindgut isolate Acetonema longum, strain TmPN3T is proposed as the type species of a new genus, Sporotalea
propionica gen. nov. sp. nov. (DSM 13327T, ATCC BAA-626T). 相似文献
287.
Metabolism of ammonia (NH3) and hydroxylamine (NH2OH) by wild-type and a nitrite reductase (nirK) deficient mutant of Nitrosomonas europaea was investigated to clarify the role of NirK in the NH3 oxidation pathway. NirK-deficient N. europaea grew more slowly, consumed less NH3, had a lower rate of nitrite (NO2
−) production, and a significantly higher rate of nitrous oxide (N2O) production than the wild-type when incubated with NH3 under high O2 tension. In incubations with NH3 under low O2 tension, NirK-deficient N. europaea grew more slowly, but had only modest differences in NH3 oxidation and product formation rates relative to the wild-type. In contrast, the nirK mutant oxidized NH2OH to NO2
− at consistently slower rates than the wild-type, especially under low O2 tension, and lost a significant pool of NH2OH–N to products other than NO2
− and N2O. The rate of N2O production by the nirK mutant was ca. three times higher than the wild-type during hydrazine-dependent NO2
− reduction under both high and low O2 tension. Together, the results indicate that NirK activity supports growth of N. europaea by supporting the oxidation of NH3 to NO2
− via NH2OH, and stimulation of hydrazine-dependent NO2
− reduction by NirK-deficient N. europaea indicated the presence of an alternative, enzymatic pathway for N2O production. 相似文献
288.
The formation of oxidized proteins is one of the highlights of oxidative stress. In order not to accumulate such proteins have to be degraded. The major proteolytic system responsible for the removal of oxidized proteins is the proteasome. The proteasome is distributed throughout the cytosolic and nuclear compartment of mammalian cells, with high concentrations in the nucleus. On the other hand a major part of protein oxidation is taking place in the cytosol. The present review highlights the current knowledge on the intracellular distribution of oxidized proteins and put it into contrast with the concentration and distribution of the proteasome. 相似文献
289.
Arsenite oxidation by the facultative chemolithoautotroph NT-26 involves a periplasmic arsenite oxidase. This enzyme is the first component of an electron transport chain which leads to reduction of oxygen to water and the generation of ATP. Involved in this pathway is a periplasmic c-type cytochrome that can act as an electron acceptor to the arsenite oxidase. We identified the gene that encodes this protein downstream of the arsenite oxidase genes (aroBA). This protein, a cytochrome c552, is similar to a number of c-type cytochromes from the α-Proteobacteria and mitochondria. It was therefore not surprising that horse heart cytochrome c could also serve, in vitro, as an alternative electron acceptor for the arsenite oxidase. Purification and characterisation of the c552 revealed the presence of a single heme per protein and that the heme redox potential is similar to that of mitochondrial c-type cytochromes. Expression studies revealed that synthesis of the cytochrome c gene was not dependent on arsenite as was found to be the case for expression of aroBA. 相似文献
290.
[MnL](ClO4)2 (L = N,N′,N″-tris(2-hydroxypropyl)-1,4,7-triazacyclononane) has been tested for catalyzing sulfide oxidation. In the presence of this complex, ethyl phenyl sulfide, butyl sulfide and phenyl sulfide are completely oxidized to the corresponding sulfoxides and sulfones with H2O2 as the oxidant. 2-Chloroethyl phenyl sulfide oxidation yield 2-chloroethyl phenyl sulfone and phenyl vinyl sulfone. In ethyl phenyl sulfide oxidation, effects of complex and H2O2 concentration and temperature on the reaction rate have been discussed. Through controlling reaction conditions, ethyl phenyl sulfoxide and ethyl phenyl sulfone may be produced selectively. The UV–Vis and electron paramagnetic resonance (EPR) studies on catalyst solution indicate that metal centre of the complex is transformed from Mn(II) to Mn(IV) after the addition of H2O2. At 25 °C, rate constant for ethyl phenyl sulfide oxidation is 4.38 × 10−3 min−1. 相似文献