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)

In plants the carbohydrate state provides signals to adjust metabolism to specific physiological conditions. Storage-active sink organs like seeds often contain high levels of sucrose. In order to change the sugar status during seed development a yeast-derived invertase gene was expressed in Vicia narbonensis under control of the LeguminB4 promoter. A signal sequence targeted the invertase to the apoplast in maturing embryos. In the cotyledons, sucrose was decreased whereas hexoses strongly accumulated. There was a major reduction of starch whereas proteins were less affected. Vacuoles of cotyledon cells were enlarged and dry seeds wrinkled. Transcripts and enzyme activity of sucrose synthase, the small and large subunit of ADP-glucose pyrophosphorylase as well as vicilin were downregulated. Sucrose phosphate synthase and legumin-mRNAs were not affected. Analysing single seeds with different sucrose levels revealed a positive correlation of sucrose concentration to mRNA levels of sucrose synthase and most pronounced to ADP-glucose pyrophosphorylase-mRNA levels as well as to starch content. Glucose on the other hand did not show any correlation. After feeding 14C-sucrose in vitro, the invertase-expressing cotyledons partitioned less carbon into starch compared to the wild-type. In the transgenic cotyledons, a relatively higher amount was directed into proteins compared to starch. We conclude that starch accumulation in developing cotyledons could be a function of sucrose concentration. Our results are consistent with a possible sucrose-mediated induction of storage-associated differentiation indicated by upregulation of specific genes of the starch synthesis pathway.
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PMID:Expression of a yeast-derived invertase in developing cotyledons of Vicia narbonensis alters the carbohydrate state and affects storage functions. 983 63

Sugar beet molasses is a natural resource for various products used in daily life, ranging from sucrose to amino acids for pharmaceutical industry. The separation of molasses into these high value components is performed on a large scale by ion exchange/exclusion chromatography. A biosensor system was set up for the "in time" analysis of serine and sucrose during molasses desugarisation. D-Serine was analysed with the multi-enzyme system D-serine dehydratase/lactic dehydrogenase and photometric detection of the NADH consumed. Sucrose was determined with invertase/mutarotase/glucose oxidase and the oxygen consumed was monitored amperometrically. An analysis could be performed within 2-5 min by directly injecting samples from the chromatographic process into the flow injection analysis system. The determination range for the sucrose analysis was 0-2.5 gl-1 and for the analysis of D-serine 0-0.5 gl-1. The standard deviation for the measurement of D-serine was 1.7%.
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PMID:Flow injection analysis system for the supervision of industrial chromatographic downstream processing in biotechnology. 988 58

In vitro and in situ findings suggest an impairment of digestive and absorptive functions in the small intestine by enteral cadmium salts. In the rat, diets with up to 1 mmol Cd/kg are well tolerated, however, so that the impairment might not be this drastic or compensated by adaptive changes. To elucidate whether small intestinal functions are altered, we studied the effect of dietary cadmium on the longitudinal pattern of mucosal enzymes and the in vitro uptake of methyl alpha-D-glucoside in the small intestine of female rats. Three groups of rats were employed, a control group and two groups receiving dietary CdCl2 either at 0.3 or 1.0 mmol Cd/kg of diet. Rats were killed after 1 week of feeding. The entire small intestine was removed, rinsed with ice-cold saline and divided into 12 segments of equal length. Mucosal scrapings from each segment were used to measure mucosal cadmium levels, sucrase, lactase, alkaline phosphatase, glycylleucine-hydrolase, and diamine oxidase activities. Sugar uptake was determined in vitro in all segments using everted rings tissue accumulation method. Although cadmium levels in the mucosa were high (>100 ng Cd/mg protein or >100 micromol Cd/kg WW) most enzyme activities were only slightly changed. When significant decreases in activity were detected, they were only observed in the proximal small intestine. Sugar uptake was also impaired only in proximal segments, the maximal transport capacity was reduced by approximately 20%. These findings suggest that cadmium even at dietary levels of 1 mmol/kg do not lead to a drastic impairment of digestive and absorptive functions in the small intestine and that in the rat presently observed, mostly proximal impairments are easily compensated by unaltered distal functions. Certainly, absorption of micronutrients, for which an impaired proximal function cannot be compensated, e.g. iron, might be critical in this respect.
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PMID:Longitudinal pattern of enzymatic and absorptive functions in the small intestine of rats after short-term exposure to dietary cadmium chloride. 1004 3

Sucrose is the photoassimilate transported from the leaves to the fruit of tomato yet the fruit accumulates predominantly glucose and fructose. Hydrolysis of sucrose entering the fruit can be accomplished by invertase or sucrose synthase. Early in tomato fruit development there is a transient increase in sucrose synthase activity and starch which is correlated with fruit growth and sink strength suggesting a regulatory role for sucrose synthase in sugar import. Using an antisense sucrose synthase cDNA under the control of a fruit-specific promoter we show that sucrose synthase activity can be reduced by up to 99% in young fruit without affecting starch or sugar accumulation. This result calls into question the importance of sucrose synthase in regulating sink strength in tomato fruit.
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PMID:Transgenic tomato plants with decreased sucrose synthase are unaltered in starch and sugar accumulation in the fruit. 1041 1

Fruits of cv. Fortune mandarin were periodically harvested throughout the ripening period to evaluate changes in carbohydrate content and metabolism in flavedo tissue and to determine the potential role of carbohydrates in the tolerance of citrus fruit to chilling injury (CI). Sucrose showed little change in the flavedo during the season, but fructose and glucose increased, in nearly equal amounts, throughout the fall and winter, reaching a maximum in January. Starch levels were less abundant than soluble carbohydrates and rose continuously until March. Sucrose phosphate synthase (SPS; EC 4.1.14) activity decreased from December throughout ripening. Changes in sucrose synthase (SS; EC 2.4.1.13) and acid and alkaline invertase (Inv; EC 3.2.1.26) activities correlated with changes in the reducing sugars, but acid invertase was less active than the other sucrose-metabolizing enzymes. Carbohydrate changes in the flavedo of Fortune mandarins with fruit maturity appear not to be related to the chilling tolerance of fruits during cold storage.
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PMID:Carbohydrate content and metabolism as related to maturity and chilling sensitivity of cv. Fortune mandarins. 1055 19

The content of free sugars and the activities of enzymes involved in carbon metabolism-sucrose synthase, acid and alkaline invertase, phosphoenol pyruvate carboxylase, malic enzyme and isocitrate dehydrogenase were determined during seed development in mungbean pods. A decrease in carbohydrate content of pod wall from 10 to 25 days after flowering (DAF) and a concomitant increase in the seed till 20 DAF was observed. Sucrose remained the dominant soluble sugar in the pod wall and seed. In the branch of inflorescence and pod wall, the activities of sucrose metabolizing enzymes, viz. acid and alkaline invertase, sucrose synthase (synthesis and cleavage) and sucrose phosphate synthase were higher at 5-10 DAF, whereas in seed the maximum activities of these enzymes were observed at the time of maximum seed filling stage (10-20 DAF). High activities of sucrose synthase at the time of rapid seed filling can be correlated to its sink strength. Higher activities of phosphoenol pyruvate carboxylase in the branch of inflorescence and pod wall than in seed may indicate the involvement of the fruiting structure for recapturing respired CO2. High activities of isocitrate dehydrogenase and malic enzyme in the seed at the time of rapid seed filling could provide NADPH and carbon skeletons required for the synthesis of various seed reserves.
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PMID:Ontogenic changes in enzymes of carbon metabolism in relation to carbohydrate status in developing mungbean reproductive structures. 1072 78

Enzymatic changes are often detrimental to quality of low-moisture foods. In the present study, effects of glass transition and water on sucrose inversion in a lactose-sucrose food model were investigated. Amorphous samples were produced by freeze-drying lactose-sucrose (2:1)-invertase (20 mg invertase/49.4 g of carbohydrate) dissolved in distilled water. Sorption isotherms were determined gravimetrically at 24 degrees C. Sucrose hydrolysis was determined by monitoring glucose content using a test kit and the amounts of fructose, glucose, and sucrose using HPLC. The glass transition temperatures, T(g), at various water contents were measured using differential scanning calorimetry (DSC). The BET and the GAB sorption models were fitted to experimental data up to a(w) 0.444 and 0.538, respectively. Water sorption and DSC results suggested time-dependent crystallization of sugars at a(w) 0.444 and above. Significant sucrose hydrolysis occurred only above T(g), concomitantly with crystallization. Sucrose hydrolysis and crystallization were not likely in glassy materials.
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PMID:Glass transition and water effects on sucrose inversion by invertase in a lactose-sucrose system. 1088 68

A study was made of the effect of the activity and purity of enzymes in the assay of total dietary fiber (AOAC Method 985.29) and specific dietary fiber components: resistant starch, fructan, and beta-glucan. In the measurement of total dietary fiber content of resistant starch samples, the concentration of alpha-amylase is critical; however, variations in the level of amyloglucosidase have little effect. Contamination of amyloglucosidase preparations with cellulase can result in significant underestimation of dietary fiber values for samples containing beta-glucan. Pure beta-glucan and cellulase purified from Aspergillus niger amyloglucosidase preparations were used to determine acceptable critical levels of contamination. Sucrose, which interferes with the measurement of inulin and fructooligosaccharides in plant materials and food products, must be removed by hydrolysis of the sucrose to glucose and fructose with a specific enzyme (sucrase) followed by borohydride reduction of the free sugars. Unlike invertase, sucrase has no action on low degree of polymerization (DP) fructooligosaccharides, such as kestose or kestotetraose. Fructan is hydrolyzed to fructose and glucose by the combined action of highly purified exo- and endo-inulinases, and these sugars are measured by the p-hydroxybenzoic acid hydrazide reducing sugar method. Specific measurement of beta-glucan in cereal flour and food extracts requires the use of highly purified endo-1,3:1,4 beta-glucanase and A. niger beta-glucosidase. Beta-glucosidase from almonds does not completely hydrolyze mixed linkage beta-glucooligosaccharides from barley or oat beta-glucan. Contamination of these enzymes with starch, maltosaccharide, or sucrose-hydrolyzing enzymes results in production of free glucose from a source other than beta-glucan, and thus an overestimation of beta-glucan content. The glucose oxidase and peroxidase used in the glucose determination reagent must be essentially devoid of catalase and alpha- and beta-glucosidase.
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PMID:Importance of enzyme purity and activity in the measurement of total dietary fiber and dietary fiber components. 1099 29

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 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.
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PMID:Regulation of sucrose metabolism in higher plants: localization and regulation of activity of key enzymes. 1100 2

Sucrose synthase (SS) activity has been suggested to be a key point of regulation in nodule metabolism since this enzyme is down-regulated in response to different stresses which lead to decreased nitrogen fixation. In soybean, a dramatic decline of SS transcripts has been observed within 1 d from the onset of drought. Such a quick response suggests mediation by a signal transduction molecule. Abscisic acid (ABA) is a likely candidate to act as such a molecule as it mediates in a significant number of plant responses to environmental constraints. The hypothesis of ABA controlling nodule metabolism was approached in this work by assessing nodule responses to exogenous ABA supply in pea. Under the experimental conditions, ABA did not affect plant biomass, nodule numbers or dry weight. However, nitrogen fixation rate was reduced by 70% within 5 d and by 80% after 9 d leading to a reduced plant organic nitrogen content. Leghaemoglobin (Lb) content declined in parallel with that of nitrogen fixation. SS activity, however, was not affected by ABA treatment, and neither were the activities of the enzymes aspartate amino transferase, alkaline invertase, malate dehydrogenase, glutamate synthase, uridine diphosphoglucose pyrophosphorylase, isocitrate dehydrogenase, and glutamine synthetase. Nodule bacteroid-soluble protein content was reduced in nodules only after 9 d of ABA treatment. These results do not support the hypothesis that ABA directly regulates SS activity. However, they do suggest the occurrence of at least two different control pathways in nodules under environmental constraints, which include ABA being involved in a Lb/oxygen-related control of nitrogen fixation.
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PMID:Abscisic acid induces a decline in nitrogen fixation that involves leghaemoglobin, but is independent of sucrose synthase activity. 1128 73


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