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1.
用Cry1Ab蛋白处理的果蝇喂养拟环纹豹蛛Pardosa pseudoannulata,在第1d、3d、5d、7d、9d、11d用酶联免疫(ELISA)检测技术测定实验组和对照组拟环纹豹蛛体内Cry1Ab蛋白含量,运用紫外分光光度法检测拟环纹豹蛛体内超氧化物歧化酶(SOD)、谷胱甘肽过氧化物酶(GSH—Px)、乙酰胆碱酯酶(AChE)的活性,探讨拟环纹豹蛛体内Cw1Ab蛋白的富集作用与其体内3种酶活性的关系。结果表明,从第ld至第7dC~IAb蛋F1在拟环纹豹蛛体内均具富集作用(P〈0.05),到第7d的时候达到最高值,达极显著差异(p〈0.01),然后逐渐降低,但仍显著高于对照(p〈0.05)。SOD酶活性总体趋势是降低的,在第7d达到最低;用Cry1Ab蛋白处理拟环纹豹蛛后其体内的AChE和GSH—Px酶活性随饲养时间的延长而增加,并均高于对照组(p〈0.05)。该研究征明Cry1Ab蛋白在拟环纹豹蛛体内具有富集效应,并且其体内Cry1Ab蛋白对其体内GSH—Px、AChE具铂一定诱导作用,对SOD酶具有一定程度的抑制作用。  相似文献   

2.
Arginine can be post-translationally incorporated from arginyl-tRNA into the N-terminus of soluble acceptor proteins in a reaction catalyzed by arginyl-tRNA protein transferase. In the present study, several soluble rat brain proteins that accepted arginine were identified after arginine incorporation by two dimensional electrophoresis and mass spectrometry. They were identified as: contrapsin-like protease inhibitor-3, α-1-antitrypsin, apolipoprotein E, hemopexin, calreticulin and apolipoprotein A-I. All of these proteins shared a signal sequence for the translocation of proteins across endoplasmic reticulum membranes. After losing the signal peptide, these proteins expose amino acids described as compatible for post-translational arginylation. Although the enzymatic system involved in arginylation is confined mainly in cytosol and nucleus, all the substrates described herein enter to the exocytic pathway co-translationally. Therefore, we postulate that the substrates for arginylation could reach the cytosol by retro-translocation and be then arginylated.  相似文献   

3.
以羧甲基壳聚糖(NCMC) 处理玉米开花期果穗,发育中籽粒的谷氨酰胺合成酶(GS) 、谷氨酸脱氢酶(GDH) 及谷丙转氨酶(GPT) 活性均明显增强,而蛋白水解酶活性下降。羧甲基壳聚糖处理离体玉米籽粒酶提取液,酶液中GDH 活性明显提高。羧甲基壳聚糖处理玉米果穗,其发育籽粒中可溶性蛋白和成熟种子中贮藏蛋白含量明显提高。这都表明,羧甲基壳聚糖对玉米氮代谢、蛋白质合成与积累具有明显的生理调节作用。  相似文献   

4.
Mild cognitive impairment (MCI) is generally referred to the transitional zone between normal cognitive aging and early dementia or clinically probable Alzheimer’s disease (AD). Most individuals with amnestic MCI eventually develop AD, which suggests that MCI may be the earliest phase of AD. Oxidative stress is observed in brain from subjects with both AD and MCI. Among others, two possibilities for elevated oxidataive stress are decreased activity or elevated expression of antioxidant enzymes, the latter as a response to the former. Accordingly, in the current study, the protein levels and activity of some antioxidant enzymes in the hippocampus of control and MCI brain were measured using Western blot analysis and spectrophotometric methods, respectively. Alterations in the levels and activity of a number of antioxidant enzymes in MCI brain compared to age-matched controls were found. These results are consistent with the hypothesis that oxidative stress may be an early event in the progression of amnestic MCI to AD. Special issue article in honor of Dr. Anna Maria Giuffrida-Stella.  相似文献   

5.
Treatment of fasted rats with relatively high doses of morphine rapidly results in depletion of hepatic glutathione (GSH) content and marked elevation of serum transaminase activity. Such morphine-induced response has been generally attributed to central nervous system mediated effects of the drug. We now report that this response might be due to a direct effect of the drug in the liver. That is, its metabolic activation to reactive electrophilic metabolite(s), by the hepatic cytochrome P-450-dependent mixed function oxidase system. Structure-activity relationships of morphine and its congeners indicate that the (-)-3-hydroxy-N- methylmorphinan moiety is linked with the potential of these opioids to deplete hepatic GSH and to raise serum transaminases in rats.  相似文献   

6.
Accumulation of l -kynurenine and quinolinic acid (QUIN) in the brain occurs after either ischemic brain injury or after systemic administration of pokeweed mitogen. Although conversion of l -[13C6]tryptophan to [13C6]-QUIN has not been demonstrated in brain either from normal gerbils or from gerbils given pokeweed mitogen, direct conversion in brain tissue does occur 4 days after transient cerebral ischemia. Increased activities of enzymes distal to indoleamine-2,3-dioxygenase may determine whether l -kynurenine is converted to QUIN. One day after 10 min of cerebral ischemia, the activities of kynureninase and 3-hydroxy-3,4-dioxygenase were increased in the hippocampus, but local QUIN levels and the activities of the indoleamine-2,3-dioxygenase and kynurenine-3-hydroxylase were unchanged. By days 2 and 4 after ischemia, however, the activities of all of these enzymes in the hippocampus as well as QUIN levels were significantly increased. Kynurenine aminotransferase activity in the hippocampus was unchanged on days 1 and 2 after ischemia but was decreased on day 4, at a time when local kynurenic acid levels were unchanged. A putative precursor of QUIN, [13C6]anthranilic acid, was not converted to [13C6]-QUIN in the hippocampus of either normal or 4-day postischemic gerbils. Gerbil macrophages stimulated by endo-toxin in vitro converted l -[13C6]tryptophan to [13Ce]QUIN. Kinetic analysis of kynurenine-3-hydroxylase activity in the cerebral cortex of postischemic gerbils showed that Vmax increased, without changes in Km. Systemic administration of pokeweed mitogen increased indoleamine-2,3-dioxygenase and kynureninase activities in the brain without significant changes in kynurenine-3-hydroxylase or 3-hydroxyanthranilate-3,4-dioxygenase activities. Increases in kynurenine-3-hydroxylase activity, in conjunction with induction of indoleamine-2,3-dioxygenase, kynureninase, and 3-hydroxyanthranilate-3,4-dioxygenase in macro-phage infiltrates at the site of brain injury, may explain the ability of postischemic hippocampus to convert l -[13C6]tryptophan to [13C6]QUIN.  相似文献   

7.
Biopsies from 15 human gliomas, five meningiomas, four Schwannomas, one medulloblastoma, and four normal brain areas were analyzed for 12 enzymes of energy metabolism and 12 related metabolites and cofactors. Samples, 0.01-0.25 microgram dry weight, were dissected from freeze-dried microtome sections to permit all the assays on a given specimen to be made, as far as possible, on nonnecrotic pure tumor tissue from the same region. Great diversity was found with regard to both enzyme activities and metabolite levels among individual tumors, but the following generalities can be made. Activities of hexokinase, phosphorylase, phosphofructokinase, glycerophosphate dehydrogenase, citrate synthase, and malate dehydrogenase levels were usually lower than in brain; glycogen synthase and glucose-6-phosphate dehydrogenase were usually higher; and the averages for pyruvate kinase, lactate dehydrogenase, 6-phosphogluconate dehydrogenase, and beta-hydroxyacyl coenzyme A dehydrogenase were not greatly different from brain. Levels of eight of the 12 enzymes were distinctly lower among the Schwannomas than in the other two groups. Average levels of glucose-6-phosphate, lactate, pyruvate, and uridine diphosphoglucose were more than twice those of brain; 6-phosphogluconate and citrate were about 70% higher than in brain; glucose, glycogen, glycerol-1-phosphate, and malate averages ranged from 104% to 127% of brain; and fructose-1,6-bisphosphate and glucose-1,6-bisphosphate levels were on the average 50% and 70% those of brain, respectively.  相似文献   

8.
Abstract: Damage to brain membrane phospholipids may play an important role in the pathogenesis of Alzheimer's disease (AD); however, the critical metabolic processes responsible for the generation and repair of membrane phospholipids affected by the disease are unknown. We measured the activity of key phospholipid catabolic and anabolic enzymes in morphologically affected and spared areas of autopsied brain of patients with AD and in matched control subjects. The activity of the major catabolic enzyme phospholipase A2 (PLA2), measured in both the presence and absence of Ca2+, was significantly decreased (−35 to −53%) in parietal and temporal cortices of patients with AD. In contrast, the activities of lysophospholipid acyltransferase, which recycles lysophospholipids into intact phospholipids, and glycerophosphocholine phosphodiesterase, which returns phospholipid catabolites to be used in phospholipid resynthesis, were increased by ∼50–70% in the same brain areas. Brain activities of enzymes involved in de novo phospholipid synthesis (ethanolamine kinase, choline kinase, choline phosphotransferase, phosphoethanolamine cytidylyltransferase, and phosphocholine cytidylyltransferase) were either normal or only slightly altered. The activities of PLA2 and acyltransferase were normal in the degenerating cerebellum of patients with spinocerebellar atrophy type 1, whereas the activity of glycerophosphocholine phosphodiesterase was reduced, suggesting that the alterations in AD brain were not nonspecific consequences of neurodegeneration. Our data suggest that compensatory phospholipid metabolic changes are present in AD brain that reduce the rate of phospholipid loss via both decreased catabolism (PLA2) and increased phospholipid resynthesis (acyltransferase and glycerophosphocholine phosphodiesterase).  相似文献   

9.
Abstract: Agmatinase, the enzyme that hydrolyzes agmatine to form putrescine and urea in lower organisms, was found in rat brain. Agmatinase activity was maximal at pH 8–8.5 and had an apparent K m of 5.3 ± 0.99 m M and a V max of 530 ± 116 nmol/mg of protein/h. After subcellular fractionation, most of the enzyme activity was localized in the mitochondrial matrix (333 ± 5 nmol/mg of protein/h), where it was enriched compared with the whole-brain homogenate (7.6–11.8 nmol/mg of protein/h). Within the CNS, the highest activity was found in hypothalamus, a region rich in imidazoline receptors, and the lowest in striatum and cortex. It is interesting that other agmatine-related molecules such as arginine decarboxylase, which synthesizes agmatine, and I2 imidazoline receptors, for which agmatine is an endogenous ligand, are also located in mitochondria. The results show the existence of rat brain agmatinase, mainly located in mitochondria, indicating possible degradation of agmatine by hydrolysis at its sites of action.  相似文献   

10.
Sucrose (Suc) plays a central role in plant growth and development. It is a major end product of photosynthesis and functions as a primary transport sugar and in some cases as a direct or indirect regulator of gene expression. Research during the last 2 decades has identified the pathways involved and which enzymes contribute to the control of flux. Availability of metabolites for Suc synthesis and ‘demand’ for products of sucrose degradation are important factors, but this review specifically focuses on the biosynthetic enzyme sucrose-phosphate synthase (SPS), and the degradative enzymes, sucrose synthase (SuSy), and the invertases. Recent progress has included the cloning of genes encoding these enzymes and the elucidation of posttranslational regulatory mechanisms. Protein phosphorylation is emerging as an important mechanism controlling SPS activity in response to various environmental and endogenous signals. In terms of Suc degradation, invertase-catalyzed hydrolysis generally has been associated with cell expansion, whereas SuSy-catalyzed metabolism has been linked with biosynthetic processes (e.g., cell wall or storage products). Recent results indicate that SuSy may be localized in multiple cellular compartments: (1) as a soluble enzyme in the cytosol (as traditionally assumed); (2) associated with the plasma membrane; and (3) associated with the actin cytoskel-eton. Phosphorylation of SuSy has been shown to occur and may be one of the factors controlling localization of the enzyme. The purpose of this review is to summarize some of the recent developments relating to regulation of activity and localization of key enzymes involved in sucrose metabolism in plants.  相似文献   

11.
More and more frequently these days, aquatic ecosystems are being stressed by nutrient enrichment, pollutants, and global warming, leading to a serious depletion in oxygen concentrations. Although a sudden, significant lack of oxygen will result in mortality, fishes can have an acute behavior (e.g., an increase in breathing rate, reduction in swimming frequency) and physiology responses (e.g., increase in oxygen delivery, and reduction in oxygen consumption) to hypoxia, which allows them to maintain normal physical activity. Therefore, in order to shed further light on the molecular mechanisms of hypoxia adaptation in fishes, the authors conduct comparative quantitative proteomics on Pelteobagrus vachelli livers using iTRAQ. The research identifies 511 acute hypoxia‐responsive proteins in P. vachelli. Furthermore, comparison of several of the diverse key pathways studied (e.g., peroxisome pathway, PPAR signaling pathway, lipid metabolism, glycolysis/gluco‐neogenesis, and amino acid metabolism) help to articulate the different mechanisms involved in the hypoxia response of P. vachelli. Data from proteome analysis shows that P. vachelli can have an acute reaction to hypoxia, including detoxification of metabolic by‐products and oxidative stress in light of continued metabolic activity (e.g., peroxisomes), an activation in the capacity of catabolism to get more energy (e.g., lipolysis and amino acid catabolism), a depression in the capacity of biosynthesis to reduce energy consumption (e.g., biosynthesis of amino acids and lipids), and a shift in the aerobic and anaerobic contributions to total metabolism. The observed hypoxia‐related changes in the liver proteome of the fish can help to understand or can be related to the hypoxia‐related response that takes place in similar conditions in the liver or other proteomes of mammals.  相似文献   

12.
ABSTRACT

Sucrose (Sue) plays a central role in plant growth and development. It is a major end product of photosynthesis and functions as a primary transport sugar and in some cases as a direct or indirect regulator of gene expression. Research during the last 2 decades has identified the pathways involved and which enzymes contribute to the control of flux. Availability of metabolites for Sue synthesis and 'demand' for products of sucrose degradation are important factors, but this review specifically focuses on the biosynthetic enzyme sucrose-phosphate synthase (SPS), and the degradative enzymes, sucrose synthase (SuSy), and the invertases. Recent progress has included the cloning of genes encoding these enzymes and the elucidation of posttranslational regulatory mechanisms. Protein phosphorylation is emerging as an important mechanism controlling SPS activity in response to various environmental and endogenous signals. In terms of Sue degradation, invertase-catalyzed hydrolysis generally has been associated with cell expansion, whereas SuSy-catalyzed metabolism has been linked with biosynthetic processes (e.g., cell wall or storage products). Recent results indicate that SuSy may be localized in multiple cellular compartments: (1) as a soluble enzyme in the cytosol (as traditionally assumed); (2) associated with the plasma membrane; and (3) associated with the actin cytoskeleton. Phosphorylation of SuSy has been shown to occur and may be one of the factors controlling localization of the enzyme. The purpose of this review is to summarize some of the recent developments relating to regulation of activity and localization of key enzymes involved in sucrose metabolism in plants.  相似文献   

13.
Abstract: Expression of the BCL-2 protein family members, BAX, BAK, BAD, BCL-xL, BCL-xS, and BCL-2, was measured (by western blotting using specific antibodies) in PC12 cells before and during apoptosis induced by either H2O2 treatment or by serum deprivation and during rescue from apoptosis by nerve growth factor (NGF). H2O2-induced apoptosis, as measured by DNA fragmentation, caused: (a) a dose-dependent increase in BAX, (b) a dose-independent increase in BAK, and (c) a dose-dependent inhibition of BAD expression. By comparison, apoptosis induced by serum deprivation resulted in a time-dependent decrease in both BAX and BAK, along with a dramatic and sudden decrease in BAD expression. However, when PC12 cells were incubated in an apoptosis-sparing medium (i.e., NGF-supplemented serum-free medium), both BAX and BAK were increased significantly, whereas BAD expression remained inhibited. BCL-xL expression was increased by H2O2 but unaffected by serum deprivation or long-term NGF treatment. Neither BCL-2 nor BCL-xS expression could be detected in PC12 cells under the experimental conditions tested. Our results show that the expression of BAX, BAK, BAD, and BCL-xL is altered in a stimulus-dependent manner but cannot be used to define whether a cell will undergo or survive apoptosis. The similarity between changes in expression of BCL-2-related proteins induced by H2O2 exposure and NGF rescue could reflect activation in part of a common antioxidant pathway.  相似文献   

14.
Ribosomal subunit assembly is initiated by the binding of several primary binding proteins. Results from chemical modification studies show that 16S ribosomal RNA undergoes striking structural rearrangements when protein S17 is bound. For the first time, we are able to distinguish and order these structural rearrangements by using time-dependent chemical probing. Initially, protein S17 binds to a portion of helix 11, inducing a kink-turn in that helix that bends helix 7 toward the S17-helix 11 complex in a hairpin-like manner, allowing helix 7 to bind to protein S17. This structural change is rapidly stabilized by interactions at the distal and proximal ends of both RNA helices. Identifying the dynamic nature of interactions between RNA and proteins is not only essential in unraveling ribosome assembly, but also has more general application to all protein-RNA interactions.  相似文献   

15.
The glucosamine-1-phosphate acetyltransferase activity but not the uridyltransferase activity of the bifunctional GlmU enzyme from Escherichia coli was lost when GlmU was stored in the absence of β-mercaptoethanol or incubated with thiol-specific reagents. The enzyme was protected from inactivation in the presence of its substrate acetyl coenzyme A (acetyl-CoA), suggesting the presence of an essential cysteine residue in or near the active site of the acetyltransferase domain. To ascertain the role of cysteines in the structure and function of the enzyme, site-directed mutagenesis was performed to change each of the four cysteines to alanine, and plasmids were constructed for high-level overproduction and one-step purification of histidine-tagged proteins. Whereas the kinetic parameters of the bifunctional enzyme appeared unaffected by the C296A and C385A mutations, 1,350- and 8-fold decreases of acetyltransferase activity resulted from the C307A and C324A mutations, respectively. The Km values for acetyl-CoA and GlcN-1-P of mutant proteins were not modified, suggesting that none of the cysteines was involved in substrate binding. The uridyltransferase activities of wild-type and mutant GlmU proteins were similar. From these studies, the two cysteines Cys307 and Cys324 appeared important for acetyltransferase activity and seemed to be located in or near the active site.  相似文献   

16.
Vertebrate vocalizations are widespread secondary sexual signals used for mate attraction and territory defence, and variation in signal quality is often condition dependent and impacts reproductive outcomes. Although vocal signal performance is known to reflect various aspects of male quality, few studies have examined the underlying mechanisms mediating its costs and hence its honesty. Using a population of Arctic‐breeding snow buntings (Plectrophenax nivalis), we compared the ‘Oxidation Handicap Hypothesis’, which predicts that testosterone‐induced increases in oxidative stress provide a direct mechanistic basis for ensuring the honesty of many secondary sexual signals, to the ‘Aerobic Activity Hypothesis, which predicts that it is the aerobic activity involved with signal production (i.e. vocal performance or defending a large territory) and not testosterone directly that links signal quality and oxidative stress. Males singing at faster rates had higher levels of both reactive oxygen metabolites and non‐enzymatic antioxidant capacity in the plasma (i.e. without an increase in overall oxidative stress), enabling certain males to produce high‐quality signals while also mitigating the costs of an associated increase in oxidative stress. However, these results were completely independent of plasma testosterone levels, supporting the role of aerobic performance in directly affecting oxidative stress. Although song performance was not linked to reproductive parameters in our data set, our research is the first to test these competing hypotheses in a behavioural trait and results suggest that oxidative stress may be an underlying physiological cost preventing low‐quality individuals from producing high‐quality signals.  相似文献   

17.
Abstract: Enzyme activities and protein levels of several protein and lipid kinases were measured in postmortem tissue from patients who died with amyotrophic lateral sclerosis (ALS) as well as from control subjects. Patients who died with ALS had increased activities and protein levels of phosphatidylinositol 3-kinase (PI 3-K) in particulate fractions of spinal cord tissue compared with control subjects. The PI 3-K activity increased with PI 3-K protein level, indicating no change in specific PI 3-K activity in ALS. No differences in PI 3-K activities were found in cytosolic fractions of spinal cord, or in motor and visual cortices, from ALS patients compared with those from controls. PI 3-K activities and protein levels were unchanged in brain tissue from patients who died with Alzheimer's disease compared with those from controls. PI 3-K is a lipid kinase that is important for cell survival and is activated in response to many growth factors. Increased PI 3-K activities in particulate fractions of spinal cord from ALS patients may be related to the increase of PI 3-K protein levels found in this tissue. The protein kinases Erk2, protein kinase B (PKB), and p70 ribosomal S6 kinase (S6K) showed no differences in activities in spinal cord tissue between ALS patients and controls. However, the amounts of PKB and S6K protein were significantly higher in ALS patients, whereas Erk2 protein amount was unchanged compared with controls. Protein kinase C activity was increased in spinal cord tissue from ALS patients, which is consistent with our previous report. The increased activity of PI 3-K in spinal cord tissue from patients with ALS implicates the involvement or activation of PI 3-K in ALS, as either a cause or a consequence of the neuron loss. The lack of up-regulation in the activities of PKB and S6K in ALS tissue supports an impairment in signal transduction cascades mediated by PI 3-K in this neurodegenerative disease.  相似文献   

18.
《Free radical research》2013,47(1-2):43-56
Comparison of the anti-inflammatory properties of superoxide dismutases from different sources using different models (carrageenan and adriamycin induced inflammation, adjuvant-induced arthritis) in rats shows a very wide range of activity from extremely good to zero. Neither circulating life time nor intracellular penetration are of importance. The mechanism of biological activity of the SODs is discussed in detail, and binding to an interphase situation on the outer cell surface is postulated. As a consequence of these various considerations it is predicted that clinical application of human Cu-SOD in humans may well be much less spectacular than is commonly assumed, and indeed may be somewhat disappointing.  相似文献   

19.
20.
Diabetes is a metabolic disorder affecting more than 400 million individuals and their families worldwide. The major forms of diabetes (types 1 and 2) are characterized by pancreatic β-cell dysfunction and, in some cases, loss of β-cell mass causing hyperglycemia due to absolute or relative insulin deficiency. The BCL-2 homology 3 (BH3)-only protein BIM has a wide role in apoptosis induction in cells. In this review, we describe the apoptotic mechanisms mediated by BIM activation in β cells in obesity and both forms of diabetes. We focus on molecular pathways triggered by inflammation, saturated fats, and high levels of glucose. Besides its role in cell death, BIM has been implicated in the regulation of mitochondrial oxidative phosphorylation and cellular metabolism in hepatocytes. BIM is both a key mediator of pancreatic β-cell death and hepatic insulin resistance and is thus a potential therapeutic target for novel anti-diabetogenic drugs. We consider the implications and challenges of targeting BIM in the treatment of the disease.  相似文献   

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