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)

Sucrose:sucrose 6-fructosyltransferase, an enzyme activity recently identified in fructan-accumulating barley (Hordeum vulgare) leaves, was further characterized. The purified enzyme catalyzed the transfer of a fructosyl group from sucrose to various acceptors. It displayed some [beta]-fructosidase (invertase) activity, indicating that water could act as fructosyl acceptor. Moreover, it transferred the fructosyl residue of unlabeled sucrose to [U-14C]Glc, producing [U-14C]sucrose and unlabeled glucose. Most significantly for fructan synthesis, the enzyme used as acceptors but not as donors a variety of oligofructans containing [beta](2->1)- and [beta](2->6)-linked fructosyl moieties. Thus, it acted as a general sucrose:fructan fructosyltransferase. The products formed by the enzyme from sucrose and various purified, structurally characterized oligofructans were analyzed by liquid chromatography and identified by comparison with structurally characterized standards. The results showed that the enzyme formed exclusively [beta](2->6) fructosyl-fructose linkages, either initiating or elongating a fructan chain of the phlein type. We propose, therefore, to rename the purified enzyme sucrose:fructan 6-fructosyltransferase.
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PMID:Sucrose:Fructan 6-Fructosyltransferase, a Key Enzyme for Diverting Carbon from Sucrose to Fructan in Barley Leaves. 1222 31

Bacterial fructosyltransferases (FTFs) are retaining-type glycosidases that belong to family 68 of glycoside hydrolases. Recently, the high-resolution 3D structure of the Bacillus subtilis levansucrase has been solved [Meng, G. and Futterer, K., Nat. Struct. Biol. 10 (2003) 935-941]. Based on this structure, the catalytic nucleophile, general acid/base catalyst, and transition state stabilizer were identified. However, a detailed characterization of site-directed mutants of the catalytic nucleophile has not been presented for any FTF enzyme. We have constructed site-directed mutants of the three putative catalytic residues of the Lactobacillus reuteri 121 levansucrase and inulosucrase and characterized the mutant proteins. Changing the putative catalytic nucleophiles D272 (inulosucrase) and D249 (levansucrase) into their amido counterparts resulted in a 1.5-4x10(5) times reduction of total sucrase activity.
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PMID:Site-directed mutagenesis study of the three catalytic residues of the fructosyltransferases of Lactobacillus reuteri 121. 1498 11

Fructan 1-exohydrolase, an enzyme involved in fructan degradation, belongs to the glycosyl hydrolase family 32. The structure of isoenzyme 1-FEH IIa from Cichorium intybus is described at a resolution of 2.35 A. The structure consists of an N-terminal fivefold beta-propeller domain connected to two C-terminal beta-sheets. The putative active site is located entirely in the beta-propeller domain and is formed by amino acids which are highly conserved within glycosyl hydrolase family 32. The fructan-binding site is thought to be in the cleft formed between the two domains. The 1-FEH IIa structure is compared with the structures of two homologous but functionally different enzymes: a levansucrase from Bacillus subtilis (glycosyl hydrolase family 68) and an invertase from Thermotoga maritima (glycosyl hydrolase family 32).
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PMID:X-ray diffraction structure of a plant glycosyl hydrolase family 32 protein: fructan 1-exohydrolase IIa of Cichorium intybus. 1565 99

Lactobacillus sanfranciscensis is a key organism of the lactic microflora in traditional and industrial sourdough fermentations. In this paper we provide evidence for the formation of heterooligosaccharides (HeOS) by L. sanfranciscensis during growth in sourdough. To identify the HeOS based on HPAEC-PAD analysis, HeOS standards were synthesized by enzymatic reactions with L. sanfranciscensis levansucrase in a chemically defined system in the presence of raffinose, maltotriose, maltose, xylose, or arabinose as acceptor carbohydrates. The oligosaccharides known to originate from the corresponding acceptor reactions, 1(F)-beta-fructosylraffinose, 1(F)-beta-fructofuranosylmaltotriose, erlose (1(F)-beta-fructofuranosylmaltose), xylsucrose, 1(F)-beta-fructosylxylsucrose, and arabsucrose, were identified by HPAEC-PAD. Evidence for the formation of further tri-, tetra-, and pentasaccharides was provided. Wheat doughs with sucrose were fermented with L. sanfranciscesis TMW 1.392 or the isogenic, levansucrase-negative strain TMW 1.392Deltalev, and the analysis of dough extracts or invertase-treated dough extracts provided evidence for the formation of arabsucrose and erlose in sourdough in addition to 1-kestose and nystose.
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PMID:Evidence for formation of heterooligosaccharides by Lactobacillus sanfranciscensis during growth in wheat sourdough. 1579 79

The endophytic Gram-negative bacterium Gluconacetobacter diazotrophicus SRT4 secretes a constitutively expressed levansucrase (LsdA, EC 2.4.1.10), which converts sucrose into fructooligosaccharides and levan. The enzyme is included in GH (glycoside hydrolase) family 68 of the sequence-based classification of glycosidases. The three-dimensional structure of LsdA has been determined by X-ray crystallography at a resolution of 2.5 A (1 A=0.1 nm). The structure was solved by molecular replacement using the homologous Bacillus subtilis (Bs) levansucrase (Protein Data Bank accession code 1OYG) as a search model. LsdA displays a five-bladed beta-propeller architecture, where the catalytic residues that are responsible for sucrose hydrolysis are perfectly superimposable with the equivalent residues of the Bs homologue. The comparison of both structures, the mutagenesis data and the analysis of GH68 family multiple sequences alignment show a strong conservation of the sucrose hydrolytic machinery among levansucrases and also a structural equivalence of the Bs levansucrase Ca2+-binding site to the LsdA Cys339-Cys395 disulphide bridge, suggesting similar fold-stabilizing roles. Despite the strong conservation of the sucrose-recognition site observed in LsdA, Bs levansucrase and GH32 family Thermotoga maritima invertase, structural differences appear around residues involved in the transfructosylation reaction.
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PMID:Crystal structure of levansucrase from the Gram-negative bacterium Gluconacetobacter diazotrophicus. 1586 70

Lactic acid bacteria (LAB) employ sucrase-type enzymes to convert sucrose into homopolysaccharides consisting of either glucosyl units (glucans) or fructosyl units (fructans). The enzymes involved are labeled glucansucrases (GS) and fructansucrases (FS), respectively. The available molecular, biochemical, and structural information on sucrase genes and enzymes from various LAB and their fructan and alpha-glucan products is reviewed. The GS and FS enzymes are both glycoside hydrolase enzymes that act on the same substrate (sucrose) and catalyze (retaining) transglycosylation reactions that result in polysaccharide formation, but they possess completely different protein structures. GS enzymes (family GH70) are large multidomain proteins that occur exclusively in LAB. Their catalytic domain displays clear secondary-structure similarity with alpha-amylase enzymes (family GH13), with a predicted permuted (beta/alpha)(8) barrel structure for which detailed structural and mechanistic information is available. Emphasis now is on identification of residues and regions important for GS enzyme activity and product specificity (synthesis of alpha-glucans differing in glycosidic linkage type, degree and type of branching, glucan molecular mass, and solubility). FS enzymes (family GH68) occur in both gram-negative and gram-positive bacteria and synthesize beta-fructan polymers with either beta-(2-->6) (inulin) or beta-(2-->1) (levan) glycosidic bonds. Recently, the first high-resolution three-dimensional structures have become available for FS (levansucrase) proteins, revealing a rare five-bladed beta-propeller structure with a deep, negatively charged central pocket. Although these structures have provided detailed mechanistic insights, the structural features in FS enzymes dictating the synthesis of either beta-(2-->6) or beta-(2-->1) linkages, degree and type of branching, and fructan molecular mass remain to be identified.
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PMID:Structure-function relationships of glucansucrase and fructansucrase enzymes from lactic acid bacteria. 1652 21

* Invertases and fructan exohydrolases (FEHs) fulfil important physiological functions in plants. Sucrose is the typical substrate for invertases and bacterial levansucrases but not for plant FEHs, which are usually inhibited by sucrose. * Here we report on complexes between chicory (Cichorium intybus) 1-FEH IIa with the substrate 1-kestose and the inhibitors sucrose, fructose and 2,5 dideoxy-2,5-imino-D-mannitol. Comparisons with other family GH32 and 68 enzyme-substrate complexes revealed that sucrose can bind as a substrate (invertase/levansucrase) or as an inhibitor (1-FEH IIa). * Sucrose acts as inhibitor because the O2 of the glucose moiety forms an H-linkage with the acid-base catalyst E201, inhibiting catalysis. By contrast, the homologous O3 of the internal fructose in the substrate 1-kestose forms an intramolecular H-linkage and does not interfere with the catalytic process. Mutagenesis showed that W82 and S101 are important for binding sucrose as inhibitor. * The physiological implications of the essential differences in the active sites of FEHs and invertases/levansucrases are discussed. Sucrose-inhibited FEHs show a K(i) (inhibition constant) well below physiological sucrose concentrations and could be rapidly activated under carbon deprivation.
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PMID:Insights into the fine architecture of the active site of chicory fructan 1-exohydrolase: 1-kestose as substrate vs sucrose as inhibitor. 1733

Glycoside hydrolases (GH) have been shown to play unique roles in various biological processes like the biosynthesis of glycans, cell wall metabolism, plant defence, signalling, and the mobilization of storage reserves. To date, GH are divided into more than 100 families based upon their overall structure. GH32 and GH68 are combined in clan GH-J, not only harbouring typical hydrolases but also non-Leloir type transferases (fructosyltransferases), involved in fructan biosynthesis. This review summarizes the recent structure-function research progress on plant GH32 enzymes, and highlights the similarities and differences compared with the microbial GH32 and GH68 enzymes. A profound analysis of ligand-bound structures and site-directed mutagenesis experiments identified key residues in substrate (or inhibitor) binding and recognition. In particular, sucrose can bind as inhibitor in Cichorium intybus 1-FEH IIa, whereas it binds as substrate in Bacillus subtilis levansucrase and Arabidopsis thaliana cell wall invertase (AtcwINV1). In plant GH32, a single residue, the equivalent of Asp239 in AtcwINV1, appears to be important for sucrose stabilization in the active site and essential in determining sucrose donor specificity.
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PMID:Structural insights into glycoside hydrolase family 32 and 68 enzymes: functional implications. 1912 63

In Zymomonas mobilis, the extracellular levansucrase (SacB) and extracellular sucrase (SacC) are involved in sucrose hydrolysis. Genes coding for these two enzymes (sacB and sacC) are arranged in a cluster in the genome and separated by a short intervening sequence. The level of sacC transcript was 12-fold higher than that of sacB transcript. On the other hand, transcript stability analysis in sucrose grown cultures revealed that the half-life of the sacB transcripts (153 s) was more than twofold higher than that of sacC transcript (66 s). The decay curves of sacB and sacC transcripts analyzed by the semi-quantitative RT-PCR correlated well with the decay curves of the respective enzyme activities. In the sacB promoter disruption mutant, Z. moblis BT2, the extracellular sucrase activity decreased from 2.6 to 2.0 U mg(-1) in sucrose medium due to the loss of SacB expression. The expression of sacC in the absence of the sacB promoter suggested that these two genes could be transcribed as different mRNAs. The promoter-lacZ fusion studies in Escherichia coli proved that the short intervening region acts as a strong promoter for the sacC gene.
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PMID:Characterization of multiple promoters and transcript stability in the sacB-sacC gene cluster in Zymomonas mobilis. 1941 38

Homopolysaccharide (glucan and fructan) synthesis from sucrose by sucrase enzymes in lactic acid bacteria (LAB) has been well studied in the genera Leuconostoc, Streptococcus and Lactobacillus. This study aimed to identify and characterize genes encoding glucansucrase/glucosyltransferase (GTF) and fructansucrases/fructosyltransferase (FTF) enzymes from genomic DNA of 'rare' Indonesian exopolysaccharide-producing LAB. From a total of 63 exopolysaccharide-producing LAB isolates obtained from foods, beverages and environmental samples, 18 isolates showing the most slimy and mucoid colony morphologies on sucrose were chosen for further study. By comparing bacterial growth on De Man, Rogosa and Sharpe (MRS)-sucrose with that on MRS-raffinose, and using the results of a previous PCR screening study with degenerate primer pairs targeting the conserved catalytic domain of GTFs, various strains were identified as producers of fructan (13), of glucan only (five) or as potential producers of both glucan and fructan (nine). Here, we report the characteristics of three gtf genes and one ftf gene obtained from Weissella confusa strains MBF8-1 and MBF8-2. Strain MBF8-1 harbored two putative gtf genes with high sequence similarity to GTFB of Lactobacillus reuteri 121 and GTF180 of L. reuteri 180, respectively. Strain MBF8-2 possessed single gtf and ftf genes with high sequence similarity to GTFKg3 of Lactobacillus fermentum Kg3 and DSRWC of Weissella cibaria, and FTF levansucrase of L. reuteri 121, respectively.
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PMID:Screening of lactic acid bacteria from Indonesia reveals glucansucrase and fructansucrase genes in two different Weissella confusa strains from soya. 1975 26


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