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:3.2.1.26 (invertase)
4,927 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The aim of this study was to investigate whether endogenous restrictions in oxygen supply are limiting for storage metabolism in developing oilseed rape (Brassica napus) seeds. Siliques were studied 30 d after flowering, when rapid lipid accumulation is occurring in the seeds. (a). By using microsensors, oxygen concentrations were measured within seeds and in the silique space between seeds. At ambient external oxygen (21% [v/v]) in the light, oxygen fell to 17% (v/v) between and 0.8% (v/v) within seeds. A step-wise reduction of the external oxygen concentration led within 2 h to a further decrease of internal oxygen concentrations, and a step-wise increase of the external oxygen concentration up to 60% (v/v) resulted in an increase in internal oxygen that rose to 30% (v/v) between and 8% (v/v) within seeds. (b). The increase in oxygen levels in the seeds was accompanied by a progressive increase in the levels of ATP, UTP, and the ATP to ADP and UTP to UDP ratios over the entire range from 0% to 60% (v/v) external oxygen. (c). To investigate metabolic fluxes in planta, 14C-sucrose was injected into seeds, which remained otherwise intact within their siliques. The increase in oxygen in the seeds was accompanied by a progressive increase in the rate of lipid (including triacylglycerol), protein and cell wall synthesis, and an increase in glycolytic flux over a range from sub- to superambient oxygen concentrations. In contrast to lipid synthesis, starch synthesis was not significantly increased at superambient oxygen levels. The levels of fermentation products such as lactate and glycerol-3P increased only at very low (0%-4% [v/v]) external oxygen concentrations. (d). When 14C-acetate or 14C-acetyl-coenzyme A (CoA) was injected into seeds, label incorporation into triacylglycerol progressively increased over the whole range of external oxygen concentrations from 0% to 60% (v/v). (e). Stimulation of lipid synthesis was accompanied by an increase in sugar levels and a decrease in the levels of hexose-phosphates and acetyl-CoA, indicating sucrose unloading and the use of acetyl-CoA as possible regulatory sites. (f). Increased lipid synthesis was also accompanied by an increase in the maximal activities of invertase and diacylglycerol acyltransferase. (g). The developmental shift from starch to lipid storage between 15 and 45 d after flowering was accompanied by an increase in the seed energy state. (h). The results show that at ambient oxygen levels, the oxygen supply is strongly limiting for energy metabolism and biosynthetic fluxes in growing rape seeds, affecting lipid synthesis more strongly than starch synthesis. The underlying mechanisms and implications for strategies to increase yield and storage product composition in oilseed crops are discussed.
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PMID:Lipid storage metabolism is limited by the prevailing low oxygen concentrations within developing seeds of oilseed rape. 1464 33

Here we investigate the role of hexoses in the metabolism of the developing potato (Solanum tuberosum) tuber by the expression of a bacterial xylose isomerase which catalyzes the interconversion of glucose and fructose. Previously, we found that glycolysis was induced in transgenic tubers expressing a yeast invertase in the cytosol and postulated that this was due either to the decreased levels of sucrose or to effects downstream of the sucrose cleavage. In the present study xylose isomerase was expressed under the control of the tuber-specific patatin promoter. Selected transformants exhibited minor changes in the levels of tuber glucose and fructose but not in sucrose. Analysis of the enzyme activities of the glycolytic pathway revealed minor yet significant increases in the maximal catalytic activities of aldolase and glyceraldehyde 3-phosphate dehydrogenase but no increase in the activities of other enzymes of glycolysis. These lines were also characterized by an elevated tuber number, glycolytic and sucrose synthetic fluxes and in some metabolite levels downstream of glycolysis. When considered together these data suggest that the perturbation of hexose levels can result in increased glycolytic and sucrose (re)synthetic fluxes in the potato tuber even in the absence of changes in the level of sucrose. The consequences of altering hexose levels in the tuber are, however, not as severe as those observed following perturbation of the level of tuber sucrose.
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PMID:Expression of a bacterial xylose isomerase in potato tubers results in an altered hexose composition and a consequent induction of metabolism. 1470 31

Major soluble proteins of grapevine ripe berries were extracted from six different cultivars including non vinifera, with trichloroacetic acid acetone and resolved in two-dimensional electrophoresis (2-DE) gels. About three hundred spots were detected on the 2-DE map after colloidal blue staining. From 2-DE map of cv. Gamay mesocarp, 67 proteins were identified (p > 0.95) using matrix-assisted laser desorption/ionization-mass spectrometry analysis. About 34%, 19%, and 13% of identified proteins play, respectively, a role in energy metabolism, defense, and stress response and primary metabolism. 2-DE analysis revealed considerable accumulation of dehydrin, invertase, and a putative transcription factor in the ripe fruit, in addition to pathogenesis-related proteins such as chitinase and thaumatin-like proteins previously documented as prevalent proteins in ripe berries. Actual translation of redundant transcripts of unclear function such as Grip31, Grip32, and Grip61 recently cloned in ripe grape berries was confirmed. The relative abundance of UDP-glucose pyrophosphorylase and vacuolar invertase strongly supported a key role of the apoplastic pathway of sugar loading during ripening. Comparative analysis shows that differences between cultivars were low, but different isoforms of alcohol dehydrogenase and of a transcription factor of hexose transporter were obvious in the six cultivars. Peptide mass fingerprinting suggests that the Adh isoforms would be Adh2/Adh6 or Adh2/Adh7 dimers and unambiguously shows that considerable deletion/insertion inside Adh7 are not cloning artifacts.
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PMID:Grape berry biochemistry revisited upon proteomic analysis of the mesocarp. 1473 Jun 82

Vegetative buds of peach (Prunus persica L. Batsch.) trees act as strong sinks and their bud break capacity can be profoundly affected by carbohydrate availability during the rest period (November-February). Analysis of xylem sap revealed seasonal changes in concentrations of sorbitol and hexoses (glucose and fructose). Sorbitol concentrations decreased and hexose concentrations increased with increasing bud break capacity. Sucrose concentration in xylem sap increased significantly but remained low. To clarify their respective roles in the early events of bud break, carbohydrate concentrations and uptake rates, and activities of NAD-dependent sorbitol dehydrogenase (SDH), sorbitol oxidase (SOX) and cell wall invertase (CWI) were determined in meristematic tissues, cushion tissues and stem segments. Only CWI activity increased in meristematic tissues shortly before bud break. In buds displaying high bud break capacity (during January and February), concentrations of sorbitol and sucrose in meristematic tissues were almost unchanged, paralleling their low rates of uptake and utilization by meristematic tissues, and indicating that sorbitol and sucrose play a negligible role in the bud break process. Hexose concentrations in meristematic tissues and glucose imported by meristematic tissues correlated positively with bud break capacity, suggesting that hexoses are involved in the early events of bud break. These findings were confirmed by data for buds that were unable to break because they had been collected from trees deprived of cold. We therefore conclude that hexoses are of greater importance than sorbitol or sucrose in the early events of bud break in peach trees.
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PMID:Trophic control of bud break in peach (Prunus persica) trees: a possible role of hexoses. 1499 62

Leaf senescence is the final stage of leaf development in which the nutrients invested in the leaf are remobilized to other parts of the plant. Whereas senescence is accompanied by a decline in leaf cytokinin content, exogenous application of cytokinins or an increase of the endogenous concentration delays senescence and causes nutrient mobilization. The finding that extracellular invertase and hexose transporters, as the functionally linked enzymes of an apolasmic phloem unloading pathway, are coinduced by cytokinins suggested that delay of senescence is mediated via an effect on source-sink relations. This hypothesis was further substantiated in this study by the finding that delay of senescence in transgenic tobacco (Nicotiana tabacum) plants with autoregulated cytokinin production correlates with an elevated extracellular invertase activity. The finding that the expression of an extracellular invertase under control of the senescence-induced SAG12 promoter results in a delay of senescence demonstrates that effect of cytokinins may be substituted by these metabolic enzymes. The observation that an increase in extracellular invertase is sufficient to delay leaf senescence was further verified by a complementing functional approach. Localized induction of an extracellular invertase under control of a chemically inducible promoter resulted in ectopic delay of senescence, resembling the naturally occurring green islands in autumn leaves. To establish a causal relationship between cytokinins and extracellular invertase for the delay of senescence, transgenic plants were generated that allowed inhibition of extracellular invertase in the presence of cytokinins. For this purpose, an invertase inhibitor was expressed under control of a cytokinin-inducible promoter. It has been shown that senescence is not any more delayed by cytokinin when the expression of the invertase inhibitor is elevated. This finding demonstrates that extracellular invertase is required for the delay of senescence by cytokinins and that it is a key element of the underlying molecular mechanism.
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PMID:Extracellular invertase is an essential component of cytokinin-mediated delay of senescence. 1510 Mar 96

Sucrose cleavage is vital to multicellular plants, not only for the allocation of crucial carbon resources but also for the initiation of hexose-based sugar signals in importing structures. Only the invertase and reversible sucrose synthase reactions catalyze known paths of sucrose breakdown in vivo. The regulation of these reactions and its consequences has therefore become a central issue in plant carbon metabolism. Primary mechanisms for this regulation involve the capacity of invertases to alter sugar signals by producing glucose rather than UDPglucose, and thus also two-fold more hexoses than are produced by sucrose synthase. In addition, vacuolar sites of cleavage by invertases could allow temporal control via compartmentalization. In addition, members of the gene families encoding either invertases or sucrose synthases respond at transcriptional and posttranscriptional levels to diverse environmental signals, including endogenous changes that reflect their own action (e.g. hexoses and hexose-responsive hormone systems such as abscisic acid [ABA] signaling). At the enzyme level, sucrose synthases can be regulated by rapid changes in sub-cellular localization, phosphorylation, and carefully modulated protein turnover. In addition to transcriptional control, invertase action can also be regulated at the enzyme level by highly localized inhibitor proteins and by a system that has the potential to initiate and terminate invertase activity in vacuoles. The extent, path, and site of sucrose metabolism are thus highly responsive to both internal and external environmental signals and can, in turn, dramatically alter development and stress acclimation.
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PMID:Sucrose metabolism: regulatory mechanisms and pivotal roles in sugar sensing and plant development. 1513 43

Recent studies have demonstrated in leaves of maize (Zea mays L.) plants submitted to a moderate water stress an early enhancement of vacuolar invertase activity that paralleled the expression of the vacuolar invertase Ivr2 gene and the accumulation of hexoses. In this paper, the direct role of abscisic acid (ABA) was checked by providing this hormone to the root medium of hydroponically grown maize plantlets. ABA supplied to 10-day-old seedlings appeared to enhance the vacuolar invertase activity within 1 h in roots and 2 h in leaves, the maximum being reached at 4 and 8 h, respectively. The Ivr2 gene expression varied accordingly, except that the maximum values were earlier. During the first 8 h of activity enhancement, hexose and sucrose concentrations were not significantly affected by ABA. The changes in activity were correlated to leaf and root ABA concentrations and they were concentration dependent in roots and leaves. In contrast, the addition of 1% glucose or polyethylene glycol, at the same osmotic potential, was ineffective on invertase activity, but glucose supply enhanced Ivr2 transcript levels, after 18 h, in a concentration-dependent manner in the leaf, whereas they were repressed at higher concentrations in intact roots. The latter result appeared specific to intact roots since similar treatments performed using excised leaf or root pieces confirmed a previous report on the enhancement of Ivr2 and Ivr1 transcript levels by glucose in roots [J. Xu et al. (1996) Plant Cell 8:1209-1220]. Therefore, ABA appears to be a strong inducer of Ivr2-invertase expression in roots and leaves.
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PMID:Regulation of vacuolar invertase by abscisic acid or glucose in leaves and roots from maize plantlets. 1517 13

Plant cell wall (CWI) and vacuolar invertases (VI) play important roles in carbohydrate metabolism, stress responses and sugar signaling. Addressing the regulation of invertase activities by inhibitor proteins (C/VIF, cell wall/vacuolar inhibitor of fructosidase), we have identified two C/VIFs from Arabidopsis thaliana. AtC/VIF1 showed specific inhibition of VI activity, whereas AtC/VIF2 inhibited both, CWI and VI. Expression analysis revealed that expression of AtC/VIF1 was restricted to specific organs, AtC/VIF2, however, was weakly expressed throughout plant development. Promoter::GUS transformants confirmed pronounced differences of tissue/cell type-specific expression between both isoforms. Growth of an AtC/VIF1 T-DNA KO mutant was unaffected, but VI activity and hexose content were slightly increased.
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PMID:In Arabidopsis thaliana, the invertase inhibitors AtC/VIF1 and 2 exhibit distinct target enzyme specificities and expression profiles. 1532 83

Wild-type tobacco (Nicotiana tabacum L.) seed development was characterized with respect to architecture and carbohydrate metabolism. Tobacco seeds accumulate oil and protein in the embryo, cellular endosperm and inner layer of the seed coat. They have high cell wall invertase (INV) and hexoses in early development which is typical of seeds. INV and the ratio of hexose to sucrose decline during development, switching from high hex to high suc, but not until most oil and all protein accumulation has occurred. The oil synthesis which coincides with the switch is mostly within the embryo. INV activity is greater than sucrose synthase activity throughout development, and both activities exceed the demand for carbohydrate for dry matter accumulation. To investigate the role of INV-mediated suc metabolism in oilseeds, genes for yeast INV and/or hexokinase (HK) were expressed under a seed-specific napin promoter, targeting activity to the apoplast and cytosol, respectively. Manipulating the INV pathway in an oilseed could either increase oil accumulation and sink strength, or disrupt carbohydrate metabolism, possibly through sugar-sensing, and decrease the storage function. Neither effect was found: transgenics with INV and/or HK increased 30-fold and 10-fold above wild-type levels had normal seed size and composition. This contrasted with dramatic effects on sugar contents in the INV lines.
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PMID:Evidence that the hexose-to-sucrose ratio does not control the switch to storage product accumulation in oilseeds: analysis of tobacco seed development and effects of overexpressing apoplastic invertase. 1536 35

The disaccharide sucrose and the cleavage products glucose and fructose are the central molecules for carbohydrate translocation, metabolism and sensing in higher plants. Invertases mediate the hydrolytic cleavage of sucrose into the hexose monomers. Plants possess three types of invertases, which are located in the apoplast, the cytoplasm and the vacuole, respectively. It has become evident that extracellular and vacuolar invertase isoenzymes are key metabolic enzymes that are involved in various aspects of the plant life cycle and the response of the plant to environmental stimuli because their substrates and reaction products are both nutrients and signal molecules. Invertases, alone or in combination with plant hormones, can regulate many aspects of the growth and development of plants from gene expression to long-distance nutrient allocation and are involved in regulating carbohydrate partitioning, developmental processes, hormone responses and biotic and abiotic interactions.
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PMID:Function and regulation of plant invertases: sweet sensations. 1556 28


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