Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Dextranase”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 109 records · Page 6Linked to original sources
PubMed2005

Diverse dextranase genes from Paenibacillus species.

Genes encoding dextranolytic enzymes were isolated from Paenibacillus strains Dex40-8 and Dex50-2. Single, similar but non-identical dex1 genes were isolated from each strain, and a more divergent dex2 gene was isolated from strain Dex50-2. The protein deduced from the Dex40-8 dex1 gene sequence had 716 amino acids, with a predicted M(r) of 80.8 kDa. The proteins deduced from the Dex50-2 dex1 and dex2 gene sequences had 905 and 596 amino acids, with predicted M(r) of 100.1 kDa and 68.3 kDa, respectively. The deduced amino acid sequences of all three dextranolytic proteins had similarity to family 66 glycosyl hydrolases and were predicted to possess cleavable N-terminal signal peptides. Homology searches suggest that the Dex40-8 and Dex50-2 Dex1 proteins have one and two copies, respectively, of a carbohydrate-binding module similar to CBM_4_9 (pfam02018.11). The Dex50-2 Dex2 deduced amino acid sequence had highest sequence similarity to thermotolerant dextranases from thermophilic Paenibacillus strains, while the Dex40-8 and Dex50-2 Dex1 deduced protein sequences formed a distinct sequence clade among the family 66 proteins. Examination of seven Paenibacillus strains, using a polymerase chain reaction-based assay, indicated that multiple family 66 genes are common within this genus. The three recombinant proteins expressed in Escherichia coli possessed dextranolytic activity and were able to convert ethanol-insoluble blue dextran into an ethanol-soluble product, indicating they are endodextranases (EC 3.2.1.11). The reaction catalysed by each enzyme had a distinct temperature and pH dependence.

Amino Acid Sequence↗
PubMed1978

Volume changes during enzyme reactions. The influence of pressure on the action of invertase, dextranase and dextransucrase.

The pressure dependence of the maximum velocities and the Michaelis constants for the enzymes invertase and dextranase was measured up to 1400 bar. The corresponding activation volumes deltaV not equal to c and deltaV not equal to Km proved to be independent of pressure. Together with data from other sources the meaning of deltaV not equal to c and deltaV not equal to Km is established and the volume profiles of the reactions are constructed. These profiles are similar in contour to the volume profile of the dextran formation catalyzed by the enzyme dextransucrase, but the amount of the volume changes is very much larger for dextransucrase. The evaluation of salt effects shows, that for all three enzymes solvent interactions are not important in explaining the results. The reaction mechanisms seem to be governed by conformation changes of the enzymes. The larger effects in dextransucrase are explained by the produced dextran chain remaining tightly bound to the enzyme and being transported relative to the enzymes position in each reaction cycle.

Dextranase↗
PubMed1991

Cloning and expression in Escherichia coli of dextranase genes from Bacteroides thetaiotaomicron.

A genomic bank was constructed in Escherichia coli HB101, consisting of DNA fragments from Bacteroides thetaiotaomicron strain 489 inserted within the vector pBR322. By screening on complex medium containing blue dextran, 10 stable dextranase-positive (Dex+) clones were isolated. Seven groups of Dex+ inserts were identified on the basis of their restriction maps and hybridization responses. Dextanase activity of the recombinant clones was weak, and was revealed on the selection medium after 15 days. Subcloning of a Sau3AI partially digested 3.2-kb insert in the expression vector pDR720 greatly enhanced dextranse activity on blue dextran plates in one clone, but the delay remained unaltered. This suggested that the enzyme was released by cell lysis. Expression of this 0.7-kb subcloned insert was dependent on the promoter region of tryptophan operon carried by pDR720.

Bacteroides↗
PubMed1995

Cloning and sequencing of the gene coding for dextranase from Streptococcus salivarius.

We cloned and sequenced the dextranase (Dex) (1,6-alpha-glucanhydrolase; EC 3.2.1.11)-encoding gene from Streptococcus salivarius (Ss) strain M-33. Recombinant clones from an Ss genomic library specifying Dex activity were identified as colonies surrounded by transparent halos on blue dextran plates. One of the clones had a 4.3-kb KpnI fragment containing the gene coding for an 826-amino-acid polypeptide with a molecular mass of 87.9 kDa, which corresponds well to that of native Dex from the Ss culture supernatant. There was no sequence homology between the gene encoding Ss Dex and the gene encoding dextran glucosidase of S. mutans, or between their protein products.

Amino Acid Sequence↗
PubMed1975

The action pattern of Penicillium lilacinum dextranase.

The product distributions resulting from the action of Penicillium lilacinum dextranase on end-labelled oligosaccharides of the isomaltose series have been determined. The initial rates of formation of labelled products were measured for isomaltotriose up to isomalto-octaose, and the molar proportions and radioactivity of the final products from isomaltotriose up to isomaltohexaose were determined. D-Glucose was released only from isomaltotriose and isomaltotetraose, by hydrolysis of the first linkage from the reducing end (linkage 1); the terminal bonds of higher members of the series were not attacked. All oligosaccharides except isomaltotriose were hydrolyzed at more than one linkage. The main points of attack on isomaltotetraose up to isomalto-octaose were at linkage 2, and at the third linkage from the non-reducing end; these two positions coincide for isomaltopentaose. The degradation of isomaltotriose up to isomalto-octaose was entirely hydrolytic. The enzyme also catalyzed an extremely slow, concentration-dependent degradation of isomaltose, and this may have occurred via a condensation to isomaltotetraose, followed by hydrolysis of linkage 1 to give D-glucose and isomaltotriose.

Dextranase↗
PubMed1979

Modes of action of intracellular dextranase and three oligoglucanases from Pseudomonas UQM733.

The action patterns have been studied of a purified, intracellular dextranase and three intracellular alpha-D-glucosidases from Pseudomonas UQM733 on pure isomalto-oligosaccharides. The glucosidases have optimal activity on isomaltotetraose and are therefore classified as oligoglucanases. They have been used to determine the structure of two branched isomalto-oligosaccharides obtained by enzymic degradation of dextran.

Dextranase↗
PubMed1997

Cloning and characterization of a dextranase gene (dexS) from Streptococcus suis.

A gene (dexS) coding for a Streptococcus suis capsular type 2 dextranase (DexS) was detected in a recombinant gene library constructed in phage lambda ZapII, and its nucleotide sequence was determined. Sequence comparison showed that the dexS gene product had significant similarities with enzymes which hydrolyze glucose polymers. Moreover, conserved amino acids that are suggested to be part of the active site of the glucosidases are also found in DexS. The dexS gene, adjacent to the gene encoding a S. suis IgG-binding protein, encoded a protein of approximately 62 kDa which exhibited DexS activity.

Amino Acid Sequence↗
PubMed2002

An essential amino acid residue for catalytic activity of the dextranase of Streptococcus mutans.

Dextranase (Dex) is an enzyme that hydrolyzes glucan, a polymer of glucose synthesized from sucrose by glucosyltransferases (GTFs). By comparing amino acid sequences of Dexs and GTFs, we found that the Dex enzymes of Streptococcus mutans, Streptococcus sobrinus, Streptococcus downei and Streptococcus salivarius had similar amino acid sequences to those of the catalytic sites of GTFs of mutans streptococci. We therefore examined the amino acid essential in Dex catalysis by molecular genetic approaches in this study. Site-directed mutagenesis was used to convert the Asp-385 of the Dex molecule of S. mutans Ingbritt to Glu, Asn, Thr or Val. Replacement of Asp-385 with any of the amino acids resulted in complete disappearance of Dex activity. However, replacement of other Asp residues did not affect the enzyme activity. The inactive enzymes still retained dextran-binding ability. These results suggest that Asp-385 of the Dex of S. mutans Ingbritt was essential for enzyme activity and the catalytic and substrate-binding sites were located at different sites within the Dex molecule.

Amino Acid Sequence↗
PubMed2002

Analysis of a dextran-binding domain of the dextranase of Streptococcus mutans.

AIMS: To examine the dextran-binding domain of the dextranase (Dex) of Streptococcus mutans. METHODS AND RESULTS: Deletion mutants of the Dex gene of Strep. mutans were prepared by polymerase chain reaction and expressed in Escherichia coli cells. Binding of the truncated Dexs to dextran was measured with a Sephadex G-150 gel. Although the Dexs which lacked the N-terminal variable region lost enzyme activity, they still retained dextran-binding ability. In addition, further deletion into the conserved region from the N-terminal did not influence the dextran-binding ability. However, the Dex which carried a deletion in the C-terminus still possessed both enzyme activity and dextran-binding ability. Further deletion into the conserved region from the C-terminal resulted in complete disappearance of both enzyme and dextran-binding activities. CONCLUSIONS: Deletion analysis of the Dex gene of Strep. mutans showed that the C-terminal side (about 120 amino acid residues) of the conserved region of the Dex was essential for dextran-binding ability. SIGNIFICANCE AND IMPACT OF THE STUDY: The dextran-binding domain was present in a different area from the catalytic site in the conserved region of the Dex molecule. The amino acid sequence of the dextran-binding domain of the Dex differed from those of glucan-binding regions of other glucan-binding proteins reported.

Amino Acid Sequence↗
PubMed2002

Preparation and crystallization of selenomethionyl dextranase from Penicillium minioluteum expressed in Pichia pastoris.

Dextranase from the fungus Penicillium minioluteum hydrolyses alpha-1,6-glycosidic bonds in dextran polymers. The enzyme has been expressed in Pichia pastoris in the presence of selenomethionine (SeMet). The level of SeMet incorporation was estimated by amino-acid analysis to be 50%. The protein has been crystallized in space group P2(1)2(1)2, with unit-cell parameters a = 103.6, b = 115.3, c = 49.8 A and one molecule per asymmetric unit. The crystals diffract to 2.0 A and the presence of SeMet in the crystals has been confirmed by an X-ray absorption spectrum.

Crystallization↗
PubMed1982

Isolation and properties of dextranases from Bacteroides oralis Ig4a.

Extracellular dextranases were extracted from a dextran-degrading microorganism, Bacteroides oralis Ig4a, which had been isolated from human dental plaque, and purified. Crude enzyme preparations obtained from a broth culture supernatant by salting out with ammonium sulfate were subjected to column chromatography on DEAE-cellulose and subsequent Bio-Gel p-100, followed by isoelectric focusing. Two kinds of enzyme preparations, Enzymes I and II, with the ability to degrade soluble dextran were obtained. The optimal pHs of Enzymes I and II were 5.5 and 6.8, and the isoelectric points were pH 4.5 and 6.5, respectively. The molecular weights of Enzymes I and II were estimated by SDS-PAGE to be 44,000 and 52,000. Both enzymes were inhibited by Pb2+ and Fe3+, but not by Ca2+, Mg2+, Zn2+, or Fe2+. Neither the presence of EDTA nor iodoacetamide had any appreciable effect on the enzyme activity. The enzyme activity was independent of any of these metal ions. Enzyme I liberated glucose, isomaltose, maltotriose and higher oligosaccharides from dextran. In contrast, Enzyme II liberated only glucose from dextran and was assumed to be an exoglycosidase. Neither of the enzymes degraded modified insoluble glucan, which is a partially oxidized mutan of S. mutans containing predominantly alpha-(1,3) linkages.

Bacteroides↗
PubMed1992

Characterization of the dextranase purified from Streptococcus mutans Ingbritt.

We purified dextranase from the culture supernatant of Streptococcus mutans Ingbritt by procedures including ammonium sulfate precipitation, ion-exchange chromatography, and gel filtration. The molecular weight of the enzyme was estimated as 78 kDa by SDS-PAGE. The enzyme degraded dextran at the optimum pH of 5.5, but not other glucans and fructans at all. Paper chromatographic analysis revealed that the enzyme cleaved dextran by an endo-type mechanism. The enzyme was inhibited by Hg2+, Fe3+, Zn2+, and anionic detergents SDS and deoxycholic acid, but not inhibited by non-ionic detergents Triton X-100, Lubrol PX, Nonidet P-40, and Tween 80. SDS-blue dextran-PAGE analysis of the culture supernatant revealed that the enzyme activity detected in the 96 kDa band shifted gradually to the 78 kDa band during handling the supernatant. This shift was inhibited by phenylmethylsulfonyl fluoride, suggesting that the shift of the molecular size is due to proteolytic degradation of the enzyme by serine protease.

Detergents↗
PubMed1995

Characterization of the dextranase gene (dex) of Streptococcus mutans and its recombinant product in an Escherichia coli host.

The gene (dex), which encodes the Streptococcus mutans dextranase (Dex), was cloned in Escherichia coli. The E. coli host harboring a recombinant plasmid (pSD2) containing an 8-kb BamHI insert produced a Dex protein of 133 kDa as well as smaller enzymes of 118, 104, and 88 kDa. The Dex produced by the recombinant E. coli was apparently located in the cytoplasmic fraction, not in the periplasmic nor the extracellular fractions. Subcloning and deletion analysis of pSD2 showed that the structural gene of Dex was encoded by a 4-kb BamHI-SalI fragment. The fragment also contained the dex promoter which was effective in the E. coli cell.

Cloning, Molecular↗
PubMed1975

Effect of dextranase on the extracellular polysaccharide synthesis of Streptococcus mutans; chemical and scanning electron microscopy studies.

A dextranase preparation (AD17) partially purified from a culture liquor of Spicaria violacea strain IFO 6120 significantly inhibited the formation of artifcial dental plaque on a steel wire or on an extracted tooth surface. Changes in the surface morphology of Streptococcus mutans cells due to AD17 action were studied using scanning electron microscopy. S. mutans cells grown in 5% sucrose-containing broth were coated with sticky amorphous capsule-like material, whereas cells grown in sucrose in the presence of AD17 or in glucose instead of sucrose did not synthesize such capsular material. AK17 degraded commercially available dextrans of molecular weight 7 X 1(04) and 2 X 10(6) to liberate glucose and various oligosaccharides, including isomaltose. On the other hand, AD17 hydrolyzed the extracellular polysaccharides (mainly glucan in nature) of some strains of S. mutans to a limited degree. Only 15 to 36% of the total polysaccharides were hydrolyzed by AD1M with little release of isomaltose. Prolonged incubation of the polysaccharides from S. mutans with AD17 did not release additional reducing sugars, which indicates that AD17 did not contain alpha-1,3-glucanase activity. These results suggest that glucosidic linkages which are susceptible to AD17 may play an important role in the adherence of S. mutans cells to smooth surfaces.

Dental Plaque↗
PubMed1974

Evaluation of dextranase production by the cariogenic bacterium Streptococcus mutans.

A recently developed blue dextran-agar assay was utilized to detect dextranase production by a large number of strains of Streptococcus mutans. An extract obtained from S. mutans strain B2 hydrolyzed high-molecular-weight radioactive dextran to oligosaccharides. There are several possible roles for this enzyme activity in the metabolism of S. mutans dextrans.

Chromatography, Gel↗
PubMedDate not supplied

Analysis of the dextranase activity produced by an oral strain of Bacteroides ochraceus.

An anaerobic, gram-negative, dextranase-producing filamentous bacterium isolated from human dental plaque has been identified as a strain of Bacteroides ochraceus. The inducible intracellular dextran-degrading activities produced by this microoranism can be fractionated into endohydrolytic and exohydrolytic enzymes with distinct pH optima. These enzymes reduce the apparent rate of glucan production from sucrose by the dextransucrase produced by Streptococcus mutans and consequently may influence the in vivo production of polysaccharides involved in plaque accumulation and metabolism.

Bacteroides↗
PubMed1994

Effective production of glycosyl-steviosides by alpha-1,6 transglucosylation of dextrin dextranase.

Dextrin dextranase (EC 2.4.1.2; DDase), which is produced by Acetobacter capsulatus ATCC 11894, acted on a mixture of stevioside and starch hydrolysate with isoamylase, so that the enzyme was found to convert stevioside to predominantly mono-glucosyl-stevioside (SG1) and di-glucosyl-stevioside (SG2), and little of the stevioside initially added remained. SG1 was separated into two compounds (SG1a and SG1b) by reversed-phase high-pressure liquid chromatography. The structures of SG1a, SG1b, and SG2 were analyzed and concluded to be 13-O-(6-alpha-glucosyl-2-beta-glucosyl-beta-glucosyl)-19-O-beta-glucosyl -steviol, 13-O-[(6-alpha-glucosyl)(2-beta-glucosyl)-beta-glucosyl]-19-O- glucosyl-steviol, and 13-O-[(6-alpha-glucosyl)(6-alpha-glucosyl-2-beta- glucosyl)-beta-glucosyl]-19-O-beta-glucosyl-steviol, respectively. During the reaction for production of glycosyl-steviosides, DDase catalyzes transglucosylations from glucosyl donor compounds to stevioside to be SG1a and SG1b, and to SG1b to be SG2 rapidly forming alpha-1,6 glucosidic linkages. However transglucosylation to SG1a to be SG2 rarely occurred, and the conversions among stevioside and these glycosyl-steviosides were catalyzed by the action of DDase to transfer alpha-1,6 linked glucosyl residues, forming alpha-1,6 linkages.

Carbohydrate Conformation↗
PubMed1998

Purification and characterization of an isomaltotriose-producing endo-dextranase from a Fusarium sp.

An isomaltotriose-producing endo-dextranase was simply purified from cell-free culture broth of a Fusarium sp. by ethanol fractionation and consecutive column chromatographies using DEAE-Toyopearl and Bio-Gel P-100. The purified enzyme was judged to be homogeneous on PAGE and SDS-PAGE as well as isoelectric focusing. The molecular mass of the enzyme was estimated to be about 69 kDa by SDS-PAGE. The enzyme is an acidic protein with a pI of 4.6. The optimum pH and temperature were pH 6.5 and 35 degrees C, respectively. The enzyme was completely stable over the range of pH 4.5-11.8 at 4 degrees C for 24 h and at temperatures below 45 degrees C. Inactivation of the enzyme was found to be partial with 5 mM Cu2+, being about 70% inhibition and complete with 5 mM of Fe3+, Hg2+, Ag+ or NBS. The enzyme split dextran in an endo-lytic action to produce a large amount of isomaltotriose and a slight amount of isomaltose and glucose. The anomeric configurations of the reaction products formed by the enzyme were alpha-form, indicating that the alpha-glycoside linkages in the substrate are retained. The final yield of isomaltotriose from dextran T-2000 was about 62%.

Amino Acids↗