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PubMed1978

Effect of dextranase on plaque formation and caries development in the rat.

Plaque formation and caries development were studied in 0-M rats fed Diet 2000 and infected with S. mutans 6715 and fecal flora from older caries-active rats. Merck dextranase, Beckman dextranase or Beckman glucanase 447 were administered singly or in combination to groups of 12 rats either as an addition to the diet or as a "mouthwash" twice daily, 5 per week. All enzymes studied were associated with significant inhibition of both plaque formation and caries development, especially on the buccal and lingual surfaces.

Animals↗
PubMed1973

Detection and preliminary studies on dextranase-producing microorganisms from human dental plaque.

An enriched nutrient agar medium containing blue dextran has been utilized for the detection of dextranase-producing microorganisms in human dental plaque. When compared with the total viable anaerobic plaque flora, the proportion of these microbes in supragingival plaque from different individuals varied over a wide range. Preliminary characterization of some of the dextranase-producing microorganisms revealed a heterogeneous mixture of cell types with varying morphological and biochemical characteristics. Several bacterial isolates were tentatively identified as being members of the genus Actinomyces. An additional isolate appeared to belong to the genus Bacteroides. The dextran-degrading enzymes produced by these bacteria are extracellular, and a cell-free preparation from one of the isolates has been shown to cause extensive endohydrolytic cleavage of high-molecular-weight dextrans.

Actinomyces↗
PubMed1995

Purification, characterization, and specificity of dextranase inhibitor (Dei) expressed from Streptococcus sobrinus UAB108 gene cloned in Escherichia coli.

The dextranase inhibitor gene (dei) from Streptococcus sobrinus UAB108 was previously cloned, expressed, and sequenced. Its gene product (Dei) has now been purified as a single band with apparent molecular mass of 43 kDa, as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The specific activity of Dei increased 121-fold upon purification. Most Dei activity (91.2%) was located in the periplasmic fraction from recombinant Escherichia coli cells. Dei competitively inhibits dextranase (Dex). This competitive inhibition mechanism has been further shown by detection and recovery of the intermediate enzyme-inhibitor (Dex-Dei) complex by gel filtration technology using fast protein liquid chromatography. Calibration of their molecular masses indicated that native Dei exists as a tetramer, Dex exists as dimer, and the Dex-Dei complex consists of two Dex molecules with two Dei molecules. Deletion analysis indicates that the intact Dei molecule is essential for Dei activity but not for glucan binding and immune cross-reaction. Dei is a special kind of glucan-binding protein with ability to inhibit Dex with high specificity. It can inhibit endogenous Dex, which can make more branches in glucan with the cooperation of the glucosyltransferase GTF-I. This inhibition cause the accumulation of water-soluble glucan. The latter reaction product can inhibit plaque formation and adherence of the mutans group of streptococcal cells. Dei derived from S. sobrinus UAB108 can inhibit only Dex from S. sobrinus (serotypes d and g), S. downei (previously S. sobrinus, serotype h), and S. macacae (serotype h). This finding suggests that Dei is another important protein existing in some serotypes of the mutans group of streptococci which participates in sucrose metabolism through its interaction with Dex.

Bacterial Proteins↗
PubMedDate not supplied

[An insoluble colored substrate for dextranase assay].

An assay of dextranase (EC 3.2.1.11) was developed by using Sephadex G-200 coupled with Remazol Brilliant Blue (RBB) as an insoluble substrate. The assay procedure included incubation of suspension of the colored substrate in buffer containing enzyme under study, removal of residual insoluble substrate, and measurement of the absorbance of supernatant fluid containing colored soluble hydrolysis products at 595 nm. The procedure was examined in the screening of dextranase-forming bacilli from the microbial collection of the Institute of Biology, Ufa Research Center, RAS.

Anthraquinones↗
PubMed1991

Dextranase activity of streptococcal isolates from human dental plaques.

Streptococci were isolated from sixty human dental plaques. Of those isolates which exhibited dextranolytic activity on culture media containing dextran, three were selected for further investigation. Two of these isolates were identified as Streptococcus mitior and the other was a strain of Streptococcus mutans. The organisms were cultivated in a dialysed medium and enzyme activities isolated from culture supernatants by precipitation with ammonium sulphate, dialysis and lyophilization. Decolourized annuli surrounding wells in agar plates containing Blue Dextran 2000 provided evidence of dextranase activity present in culture supernatants, precipitated and redissolved proteins, dialysis retentates and lyophilized materials. The pH optima for the crude enzyme preparations were determined using the modified assay of Koh and Khouw (1970). Dextranases from the Streptococcus mitior isolates had optima at pH 6, and the optimal activity for the enzyme from the Streptococcus mutans isolate occurred at pH 5.5. Additional studies of the purified enzymes are necessary to increase understanding of the possible effects of these enzymes in human dental plaques.

Dental Plaque↗
PubMed1991

Effect of variation in growth conditions on the activity of dextranase inhibitor in continuous cultures of Streptococcus sobrinus.

The activity of free extracellular dextranase inhibitor was determined in strains of Streptococcus sobrinus which were grown in a chemostat under a variety of defined conditions. Maximum release of dextranase inhibitor occurred at low growth rate in glucose-limited medium at pH 6.5. Free inhibitor could not be detected when the strains were grown at high growth rate or in batch culture.

Culture Media↗
PubMed1977

[Characterization of dextranase from Penicillium purpurogenum (Ftoll)].

An extracellular dextranase (E. C. 3.2.1.11) was purified from cell-free culture filtrates of Penicillium purpurogenum (Ftoll). The enzyme was most active at pH 5,5. The dextranase was endo-type, it split quickly isomaltotetraose into two isomaltose molecules, slowly degraded isomaltotriose, and did not act on isomaltose. The rate of isomaltooligosaccharides hydrolysis was increased with the increase of the polymerization degree. Polyols obtained from isomaltooligosaccharides were split more slowly than the respective sugars. The isomaltopentaitol was split at two glucosidic linkages, 38% of hydrolyzed linkages being the second linkage from the sorbitol end of the molecule and 62% being the third one. The degree of degradation of dextrans depended on amount of 1,6 linkages. Isomaltose and tetrasaccharides of two types, 2(2)-alpha-D-glucosylmaltotriose and linear tetrasaccharide(s), are the lowest molecular weight products of exhaustive hydrolysis of branched dextrans.

Culture Media↗
PubMed1990

Rapid detection of dextranases in liquid samples.

A rapid procedure for detecting dextranases in fractions after liquid chromatography and other liquid samples has been developed. The detection is based on the hydrolysis of a very thin layer of cross-linked dextran (Sephadex). Dextranase positive and negative fractions can be distinguished within a short time.

Chromatography, Gel↗
PubMedDate not supplied

[Conditions of dextranase formation by Penicillium funiculosum 15].

The influence of the following factors on the synthesis of extracellular dextranase by Pen. funiculosum 15 has been studied: the quantity and age of the inoculum, pH of the cultivation medium, stimulants of the microbial growth, cultivation temperature and time. The optimal amount of dextranase has been found to form under the following conditions: inoculum--3 day mycelium constituting 4%, cultivation time--4 to 7 days, temperature--28 to 29 degrees C, initial pH of the medium--6.0.

Culture Media↗
PubMedDate not supplied

[Stabilization of dextranase from Penicillium funiculosum and Fusarium solani during heating and freeze-drying].

Freeze-drying of highly purified dextranse from Penicillium funiculosum and Fusarium solani was accompanied by 90% losses of enzyme activity and solubility. Many carbohydrates were tested as stabilizers, e.g. glucose, maltose, lactose, polyglucine, dextranase hydrolyzate of polyglucine as well as mannitol and ammonium sulfate. Polyglucine, its hydrolyzate, and glucose proved most effective stabilizers. The stabilizing effect of polyglucine hydrolyzate of dextranase during its heating and freeze-drying was compared. The effective concentration of the stabilizer during freeze-drying was 10 times lower than during heating.

Dextranase↗
PubMed1981

Induction and persistence of B-cell tolerance to the thymus-dependent component of the alpha(1 leads to 6) glucosyl determinant of dextran. Recovery induced by treatment with dextranase in vivo.

A direct comparison was made between thymus-dependent (TD) and thymus-independent (TI) responses in mice tolerized for (1 leads to 6) glycosyl determinants by the injection of dextran B512. Long-lasting B-cell tolerance by dextran was reversed when mice were treated with dextranase in vivo. Complete or partial reversion of tolerance with the enzyme was invariably obtained for the TI response but the TD component proved to be more resistant and dependent on the immunogen used to test the reversion. The uniformity of the spectrotype in BALB/c mice, even under conditions of partial tolerance, permitted the analysis by isoelectric focussing of serum from tolerant mice treated with dextranase and immunized with TD dextran-ovalbumin. Results showed that, with one single exception, mice thus treated produced spectrotypes no different from the pattern normally found in immune animals. The results presented suggest that at least some alpha(1 leads to 6) specific B cells, both TD and TI, persist in tolerized mice for at least 2 weeks after tolerance induction and they do not support the concept of clonal elimination for either TI or TD responses in adult mice.

Animals↗
PubMed1984

Effect of dextranase and protease enzymes on aggregation of Streptococcus mutans: colorimetric and electron microscopic studies.

Sucrose-induced aggregation of Streptococcus mutans was ascertained by measuring the decrease in optical density of a cell suspension after 20 h incubation. The optimum sucrose concentration for the aggregation assay was 5% w/v, at an incubation temperature of 37 degrees C. Dextranase and protease enzymes were added to the suspensions to determine their effects on aggregation. Dextranase treatment decreased aggregation. Electron microscopic studies revealed a reduction in the amount of a diffuse coat which surrounded cells in the absence of the enzyme but in the presence of sucrose, and a degradative effect on fibrous extracellular material. Protease treatment of suspensions produced an increase in optical density; cell aggregates were not apparent. Electron microscopic studies revealed extensive cell damage and lysis. The success of these enzymes in decreasing aggregation would indicate a role in both caries and plaque control in vivo.

Colorimetry↗
PubMedDate not supplied

[Hydrolysis of streptococcal polysaccharides by micromycete dextranases].

The effect of dextranase enzyme preparations obtained from Penicillium piscarium BIM G-102, Penicillium funiculosum, Aspergillus insuetus G-116 and Aspergillus ustus on polysaccharides synthesized by cariesogenic Streptococcus sanguis and Streptococcus mitis was being studied. According to the data obtained dextranases from P. piscarium, P. funiculosum and Asp. ustus can be considered as a promising anticarious agent.

Aspergillus↗
PubMedDate not supplied

[Carbohydrate component of Penicillium funiculosum dextranase].

The carbohydrate composition of dextranase from Penicillium funiculosum 15, as well as the composition of products of dextran deep hydrolysis by the enzyme were studied. The products are normally used to stabilize the enzyme during its purification. Using the methods available, it was possible to identify only part of strongly bound (adsorbed) carbohydrates. It was found that dextranase from Pen. funiculosum 15 contained two types of carbohydrates strongly bound with protein: adsorbed and covalently bound carbohydrates. A procedure allowing a complete separation of adsorbed carbohydrates was developed. The procedure is based on the use of stabilizing additives of readily separable carbohydrates. The enzyme, which is shown by polyacrylamide gel electrophoresis in the presence of Na-dodecyl sulfate and beta-mercaptoethanol to be homogeneous, consists of 313 amino acid residues, 3 glucosamine residues and residues of mannose, galactose and fucose in the ratio 6:2:1.

Adsorption↗
PubMed2005

Kinetic studies of site-directed mutational isomalto-dextranase-catalyzed hydrolytic reactions on a 27 MHz quartz-crystal microbalance.

A quartz-crystal microbalance (QCM) technique was applied to analyze effects of site-directed mutagenesis of a glycosidase (isomalto-dextranase) on the hydrolysis mechanism of the substrate binding (k(on), k(off), and K(d)) and the catalytic process (k(cat)), separately, by using a dextran-immobilized QCM in buffer solution. D266N, D198N, and D313N mutants, which are predicted as critical residues of the isomalto-dextranase hydrolytic activity, dramatically decreased the apparent enzyme activity. The D266N mutant, however, did not change the substrate binding ability (K(d)), and the D198N and D313N mutants largely increased K(d) values due to the increase of k(off) and/or the decrease of k(on) values, as well as the negatively small k(cat) values. From these results, we estimate the reaction mechanism, in which Asp266 acts as only a general acid in the catalytic process, Asp198 acts as both nucleophile in the catalytic process and binding the substrate, and Asp313 acts as only the substrate binding.

Amino Acid Sequence↗
PubMed1981

Molecular basis of auxin-regulated extension growth and role of dextranase.

The first step in the extension growth of the plant cell is a process in which the cell wall becomes ductile or plastic, after which the actual enlargement takes place passively under the influence of turgor. The nature of this process has not been explained, although much research has been carried out concerning it. In the present report, it is shown that a specific enzyme, which is identical or nearly so with dextranase (alpha-1,6-D-glucan 6-glucanohydrolase, EC 3.2.1.11) and is associated with the cell walls of growing coleoptiles, plays a prominent role in this process. The action of this enzyme is dependent on the level of growth hormone, auxin, in the tissue. Under its action, certain cell wall components are broken down to yield arabinose and glucose. These sugars are also released during autolysis of cell wall material. The molecular linkages broken in the process are probably the arabinogalactan crosslinks of the hemicellulose matrix, which are the main constituents of the wall containing arabinose. This is substantiated by the finding that dextranase can break down arabinan and compounds containing arabinose chains with the release of arabinose, just as in the action of the enzyme on the wall. The breaking of these crosslinks will impart the necessary plasticity to the wall for cell extension to occur.

Journal Article↗
PubMed2001

Isolation of a new Thermoanaerobacterium thermosaccharolyticum strain (FH1) producing a thermostable dextranase.

A Gram-positive spore-forming thermophilic strict anaerobic bacterium, designated FH1, was isolated from enrichments at 65 degrees C with dextran as sole carbon and energy source. A sequence analysis of the 16S rRNA gene revealed 99.2% identity of FH1 to Thermoanaerobacterium thermosaccharolyticum. Furthermore, the substrate spectra of both organisms were similar. It was therefore concluded that FH1 represents a new strain within the species T. thermosaccharolyticum. The optimal growth temperature of strain FH1 was 68 degrees C. The isolated organism produced a thermostable and thermoactive dextranase with a native molecular mass of approximately 200,000 Da. The enzyme was concentrated from the cell-free culture supernatant by ammonium sulfate precipitation. The resulting crude dextranase exhibited optimal activity from 65 to 70 degrees C and a pH optimum of 5.5.

Journal Article↗
PubMed1977

Degradation of polysaccharides by endo- and exoenzymes: dextran-dextranase model systems.

Experiments were carried out on dextran-dextranase systems to test the prediction of a mechanistic model recently proposed by us, for the synergistic effect of combined exo/endo enzymic action in the degradation of polymeric substrates. Soluble forms of the substrate were used. Preliminary experiments with an insoluble form of the substrate were also carried out to demonstrate the applicability of the analytical techniques to these cases. Molecular weight distributions of the degradation products were determined (by gel-permeation chromatography) and the rates of production of glucose and of other reducing sugars were also measured. It was found that the exodextranase alone had very little effect on the molecular weight distributions compared to a significant shift towards lower molecular weights obtained with the endodextranase which was synergistically enhanced by the action of the combined enzymes. Glucose was produced more rapidly by the exoenzyme compared to the endoenzyme, but combinations of the two enzymes gave a rate enhancement greater than the linear sum of the effects of the two individual enzymes. In comparing the degradation indices and polydispersities of the various degradation products, similar synergistic effects of the combined enzymes in accordance with the theoretical predictions, were observed. The practical implications of these findings to the design of fermentation processes which depend on the action of endo- and exoenzyme mixtures are noted.

Dextranase↗