PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “GLUCOSYLTRANSFERASES”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

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

At least 955 records · Page 53Linked to original sources

Collagen synthesis and types I, III, IV, and VI collagens in an animal model of disc degeneration.

STUDY DESIGN: The present study sought to elucidate the changes that occur in collagen chemistry in the early phases of disc degeneration. OBJECTIVE: To monitor the healing process of the injured anulus fibrosus and the secondary degenerative reactions in the nucleus pulposus. SUMMARY OF BACKGROUND DATA: Despite the importance of collagen chemistry under pathologic conditions in the intervertebral disc, knowledge of this aspect is very limited. METHODS: Fourteen pigs were stabbed with a scalpel blade in the anterior part of the anulus fibrosus of a lumbar disc. The animals were killed 2 weeks to 5 months after injury. The activities of prolyl 4-hydroxylase and galactosylhydroxylysyl glucosyltransferase, the total collagen content, and staining patterns for Types I, III, IV, and VI collagens were analyzed from different parts of the disc. RESULTS: The most active phase of the healing process, assessed from the activities of enzymes involved in collagen biosynthesis, took place during the first month postoperatively. The anular lesion was found to cicatrize through formation of disorganized granulation tissue in which Type I, III, and, IV collagens were deposited. In the nucleus pulposus, activities of prolyl 4-hydroxylase and galactosylhydroxylysyl glucosyltransferase and total collagen content increased, and the originally rounded cells became more elongated, resembling fibroblasts. CONCLUSIONS: The results of this study suggest that the altered composition of collagens observed in the degenerate porcine nucleus pulposus results from changes in cell phenotype: Notochondral cells were replaced by fibroblast-like cells. It is likely that trauma to the anulus fibrosus can initiate a progressive degenerative process in the disc tissue.

Animals↗

Regulation of glucosyl- and fructosyltransferase synthesis by continuous cultures of Streptococcus mutans.

Streptococcus mutans strains Ingbritt, and its derivative B7 which had been passaged through monkeys, have been used to investigate how the synthesis of extracellular glucosyl- and fructosyltransferases is regulated. The most active enzyme from carbon-limited continuous cultures was a fructosyltransferase; enzymes catalysing the formation of water-insoluble glucans from sucrose were relatively inactive. Dextransucrase (EC 2.4.1.5), which catalyses soluble glucan synthesis, was most active in the supernatant fluid from cultures grown with excess glucose, fructose or sucrose, but full activity was detected only when the enzyme was incubated with both sucrose and dextran. Little dextransucrase activity was detected in carbon-limited cultures. It is concluded that glucosyl- and fructosyltransferases are constitutive enzymes in that they are synthesized at similar rates during growth with an excess of the substrate or of the products of the reactions which they catalyse. Although the Ingbritt strain was originally isolated from a carious lesion, it is now a poor source of glucosyltransferase activity. Glucosyltransferases were extremely active in cultures of a recent clinical isolate, strain 3209, and were apparently induced during growth with excess glucose.

Culture Media↗

Comparative study of Streptococcus mutans extracellular glycosyltransferases by isoelectric focusing.

Extracellular glycosyltransferases from 17 strains of Streptococcus mutans were examined by analytical isoelectric focusing. Three kinds of glucosyltransferase: highly-branched-1,6-alpha-D-glucan synthetase, 1,3-alpha-D-glucan synthetase and 1,6-alpha-D-glucan synthetase, were excreted from serotype a, d and g strains. The enzymes of serotype a strains were distinguishable from those of serotypes d and g by differences in their pI values. Serotype c, e and f strains excreted basic glucosyltransferase and acidic fructosyltransferase. Serotype b strains also excreted the glucosyl- and fructosyltransferases, but the pI values were different from those of the enzymes from the other serotypes. Thus, S. mutans strains could be divided into four groups by analytical isoelectric focusing of glycosyltransferases which corresponded well to the four genetic groups.

Glucosyltransferases↗

Functional analysis of the O antigen glucosylation gene cluster of Shigella flexneri bacteriophage SfX.

Previous studies have shown that Shigella flexneri bacteriophage X (SfX) encodes a glucosyltransferase (GtrX, formerly Gtr), which is involved in O antigen modification (serotype Y to serotype X). However, GtrX alone can only mediate a partial conversion. More recently, a three-gene cluster has been identified next to the attachment site in the genome of two other S. flexneri bacteriophages (i.e. SfV and SfII). This gene cluster was postulated to be responsible for a full O antigen conversion. Here it is reported that besides the gtrX gene, the other two genes in the gtr locus of SfX were also involved in the O antigen modification process. The first gene in the cluster (gtrA) encodes a small highly hydrophobic protein which appears to be involved in the translocation of lipid-linked glucose across the cytoplasmic membrane. The second gene in the cluster (gtrB) encodes an enzyme catalysing the transfer of the glucose residue from UDP-glucose to a lipid carrier. The third gene (gtrX) encodes a bacteriophage-specific glucosyltransferase which is largely responsible for the final step, i.e. attaching the glucosyl molecules onto the correct sugar residue of the O antigen repeating unit. A three-step model for the glucosylation of bacterial O antigen has been proposed.

Blotting, Western↗

Amylase-binding proteins A (AbpA) and B (AbpB) differentially affect colonization of rats' teeth by Streptococcus gordonii.

Streptococcus gordonii produces two alpha-amylase-binding proteins, AbpA and AbpB, that have been extensively studied in vitro. Little is known, however, about their significance in oral colonization and cariogenicity (virulence). To clarify these issues, weanling specific pathogen-free Osborne-Mendel rats, TAN : SPFOM(OM)BR, were inoculated either with wild-type strains FAS4-S or Challis-S or with strains having isogenic mutations of abpA, abpB, or both, to compare their colonization abilities and persistence on the teeth. Experiments were done with rats fed a sucrose-rich diet containing low amounts of starch or containing only starch. The mutants and wild-types were quantified in vivo and carious lesions were scored. In 11 experiments, S. gordonii was a prolific colonizer of the teeth when rats were fed the sucrose (with low starch)-supplemented diet, often dominating the flora. Sucrose-fed rats had several-fold higher recoveries of inoculants than those eating the sucrose-free, starch-supplemented diet, regardless of inoculant type. The strain defective in AbpB could not colonize teeth of starch-only-eating rats, but could colonize rats if sucrose was added to the diet. Strains defective in AbpA surprisingly colonized better than their wild-types. A double mutant deficient in both AbpA and AbpB (abpA/abpB) colonized like its wild-type. Wild-types FAS4-S and Challis-S had no more than marginal cariogenicity. Notably, in the absence of AbpA, cariogenicity was slightly augmented. Both the rescue of colonization by the AbpB- mutant and the augmentation of colonization by AbpA- mutant in the presence of dietary sucrose suggested additional amylase-binding protein interactions relevant to colonization. Glucosyltransferase activity was greater in mutants defective in abpA and modestly increased in the abpB mutant. It was concluded that AbpB is required for colonization of teeth of starch-eating rats and its deletion is partially masked if rats eat a sucrose-starch diet. AbpA appears to inhibit colonization of the plaque biofilm in vivo. This unexpected effect in vivo may be associated with interaction of AbpA with glucosyltransferase or with other colonization factors of these cells. These data illustrate that the complex nature of the oral environment may not be adequately modelled by in vitro systems.

Animals↗

Isolation and reconstitution of cytochrome P450ox and in vitro reconstitution of the entire biosynthetic pathway of the cyanogenic glucoside dhurrin from sorghum.

A cytochrome P450, designated P450ox, that catalyzes the conversion of (Z)-p-hydroxyphenylacetaldoxime (oxime) to p-hydroxymandelonitrile in the biosynthesis of the cyanogenic glucoside beta-D-glucopyranosyloxy-(S)-p-hydroxymandelonitrile (dhurrin), has been isolated from microsomes prepared from etiolated seedlings of sorghum (Sorghum bicolor L. Moench). P450ox was solubilized using nonionic detergents, and isolated by ion-exchange chromatography, Triton X-114 phase partitioning, and dye-column chromatography. P450ox has an apparent molecular mass of 55 kD, its N-terminal amino acid sequence is -ATTATPQLLGGSVP, and it contains the internal sequence MDRLVADLDRAAA. Reconstitution of P450ox with NADPH-P450 oxidoreductase in micelles of L-alpha-dilauroyl phosphatidylcholine identified P450ox as a multifunctional P450 catalyzing dehydration of (Z)-oxime to p-hydroxyphenylaceto-nitrile (nitrile) and C-hydroxylation of p-hydroxyphenylacetonitrile to nitrile. P450ox is extremely labile compared with the P450s previously isolated from sorghum. When P450ox is reconstituted in the presence of a soluble uridine diphosphate glucose glucosyltransferase, oxime is converted to dhurrin. In vitro reconstitution of the entire dhurrin biosynthetic pathway from tyrosine was accomplished by the insertion of CYP79 (tyrosine N-hydroxylase), P450ox, and NADPH-P450 oxidoreductase in lipid micelles in the presence of uridine diphosphate glucose glucosyltransferase. The catalysis of the conversion of Tyr into nitrile by two multifunctional P450s explains why all intermediates in this pathway except (Z)-oxime are channeled.

Amino Acid Sequence↗

Synthesis of glucan on the cell surface of Streptococcus mutans: chemical and scanning electron microscopic studies.

The appearance and continuing growth of extracellular material on Streptococcus mutans HS6 cells in sucrose-containing Merthiolated buffer was observed in a scanning electron microscope and was found to be related to the glucan synthesis on the cell and to adherence of the cell to a smooth surface. Cells grown in broth completely deprived of sucrose by invertase (HS6-IV) had a characteristic, slightly rugged surface structure. On incubation of HS6-IV in the sucrose-containing buffer, a few small globular particles appeared on the surface and grew to an irregular shape (globular to fibrilar) after several hours. The increase in the total glucan content of the cells paralleled the growth of the globular material, to which ferritin-conjugated anti-dextran globulin was found to bind. On the cell surface of cells harvested from conventional broth, both small globular and irregular structures, which possibly formed from sucrose in the broth, existed originally and continued to grow during incubation, along with the material newly appearing on the surface. The accumulation of glucan on the cells resulted in their adherence to a glass surface. The inhibition of growth of the extracellular material on the cells by trypsin, dextranase or anti-glucosyltransferase corresponded to the decrease in glucan synthesis and the loss of adhering ability. These results indicated that the material growing on the cell surface was glucan synthesized by glucosyltransferases.

Adhesiveness↗

The discovery of glycogenin and the priming mechanism for glycogen biogenesis.

The biogenesis of glycogen in skeletal muscle requires a priming mechanism that has recently been elucidated. The first step is catalysed by a protein tyrosine glucosyltransferase and involves the formation of a novel glycosidic linkage, namely the covalent attachment of glucose to a single tyrosine residue (Tyr194) on a priming protein, termed glycogenin. The next stage is the extension of the glucan chain from Tyr194 and involves the sequential addition of up to seven further glucosyl residues. This reaction is brought about autocatalytically by glycogenin itself, which is a Mn2+/Mg(2+)-dependent UDP-Glc-requiring glucosyltransferase. The glucan primer is elongated by glycogen synthase, but only when glycogenin and glycogen synthase are complexed together. Glycogen synthase dissociates from glycogenin during the synthesis of a glycogen molecule, enabling glycogen molecules to reach their maximum theoretical size. Each mature glycogen beta particle in muscle contains one molecule of glycogenin attached covalently, and an average one glycogen synthase catalytic subunit bound non-covalently. As evidence accumulates that a priming protein may be a fundamental property of polysaccharide synthesis in general, the molecular details of mammalian glycogen biogenesis may serve as a useful model for other systems.

Amino Acid Sequence↗

Developmental changes in glycolipid synthesizing enzymes in the brain of a myelin-deficient mutant Wistar rat.

Changes in the activities of UDP-galactose:ceramide galactosyltransferase (CGalT, EC 2.4.1.45), UDP-glucose:ceramide glucosyltransferase (CGlcT, EC 2.4.1.80) and 3'-phosphoadenosine-5'-phosphosulfate (PAPS): galactosylceramide 3'-sulfotransferase (EC 2.8.2.11) over the myelinating period between 12 and 25 days were studied in the brains of control and myelin-deficient rats. Although the activity of galactosyltransferase with ceramides containing hydroxy fatty acids quadrupled in normal male littermates between 14 and 20 days, hardly any increase was observed in the mutant and the activity was less than 10% of control above 20 days of age. With normal fatty acid containing ceramides as acceptors, the activity decreased from 83% of the control at 12 days to approximately 30% after 20 days. Sulfotransferase activity also did not show the normal increase during the 3rd week of life and declined from 60% to 22%. Glucosyltransferase and lysosomal hydrolases in brain and ceramide galactosyltransferase in sciatic nerves appeared to be normal. These results suggest close similarities to the jimpy mutant mouse in which myelin deficiency is also inherited as an x-linked recessive trait.

Aging↗

Analysis of a primer-independent GTF-I from Streptococcus salivarius.

A glucosyltransferase (GTF) gene, designated gtfL, from Streptococcus salivarius was cloned and expressed in Escherichia coli and its nucleotide sequence determined. The GTF-L enzyme catalysed the synthesis of water-insoluble glucan in a primer-independent manner. The nucleotide sequence and derived amino acid sequence of GTF-L were similar in size and domain structure to previously sequenced glucosyltransferases. However, a 464-bp region of high variability was identified which could be selectively amplified from strains of S. salivarius by the polymerase chain reaction and could therefore form the basis for species identification. No sequence-specific motifs related to the solubility and linkage of the glucan product or its need for a dextran primer could be ascertained.

Amino Acid Sequence↗

Sucrose-derived exopolymers have site-dependent roles in Streptococcus mutans-promoted dental decay.

We have constructed a panel of mutants of S. mutans V403 which are defective in one or more of the glucosyltransferase genes (gtfB, C or D) or the fructosyltransferase gene (ftf). These strains have been tested for virulence in a gnotobiotic rat caries model with reference to both buccal (smooth surface) and sulcal (pit and fissure) carious lesions. Our data suggest differing roles for degradable and non-degradable polymers at buccal and sulcal sites. Non-degradable polymers (made by products of the gtfB and C genes) contributed significantly to the severity of smooth surface lesions. However, our studies suggested their role in pit and fissure lesions was not as important as the role of degradable polymers. Specifically, a mutant deficient in the major insoluble glucan synthesizing activity (product of the gtfB gene) was 25% more cariogenic on sulcal surfaces than was the wild-type V403 strain. We propose that extracellular glucosyltransferases and fructosyltransferase compete for sucrose and that this competition influences pathogenicity at differing tooth sites.

Animals↗

Phase I and phase II enzymes produced by Cunninghamella elegans for the metabolism of xenobiotics.

The filamentous fungus Cunninghamella elegans has the ability to metabolize xenobiotics, including polycyclic aromatic hydrocarbons and pharmaceutical drugs, by both phase I and II biotransformations. Cytosolic and microsomal fractions were assayed for activities of cytochrome P450 monooxygenase, aryl sulfotransferase, glutathione S-transferase, UDP-glucurono-syltransferase, UDP-glucosyltransferase, and N-acetyltransferase. The cytosolic preparations contained activities of an aryl sulfotransferase (15.0 nmol min-1 mg-1), UDP-glucosyltransferase (0.27 nmol min-1 mg-1) and glutathione S-transferase (20.8 nmol min-1 mg-1). In contrast, the microsomal preparations contained cytochrome P450 monooxygenase activities for aromatic hydroxylation (0.15 nmol min-1 mg-1) and N-demethylation (0.17 nmol min-1 mg-1) of cyclobenzaprine. UDP-glucuronosyltransferase activity was detected in both the cytosol (0.09 nmol min-1 mg-1) and the microsomes (0.13 nmol min-1 mg-1). N-Acetyltransferase was not detected. The results from these experiments provide enzymatic mechanism data to support earlier studies and further indicate that C. elegans has a broad physiological versatility in the metabolism of xenobiotics.

Biotransformation↗

Deletion of gtfC of Streptococcus mutans has no influence on the composition of a mixed-species in vitro biofilm model of supragingival plaque.

Glucosyltransferases from Streptococcus mutans are thought to play an important role in bacterial adherence to the tooth surface. The goal of the present study was to determine the effect of the deletion of the gtfC gene, which encodes a glucosyltransferase that catalyses primarily the formation of insoluble glucan (mutan), on colonization of S. mutans in a mixed-species biofilm model of supragingival plaque. A gtfC deletion mutant of S. mutans UA159 grew poorly in biofilms on a polystyrene surface in Todd-Hewitt medium containing sucrose, but biofilm formation in the semi-defined fluid universal medium (FUM) was not affected. The S. mutans gtfC mutant colonized with the same efficiency as the wild-type strain when grown together with five other species in a mixed-species biofilm on hydroxyapatite in a mixture of FUM and saliva with pulses of sucrose and showed the same ability to demineralize enamel in vitro. Colonization of mutant and wild-type strains was also equal in an association experiment in specific-pathogen-free rats. However, the gtfC mutant gave rise to more dentinal fissure lesions and smooth surface caries than the wild-type strain; this could be caused by a change in diffusion properties as a result of to the lack of mutan.

Animals↗

Effect of Leuconostoc mesenteroides NRRL B-512F dextransucrase carboxy-terminal deletions on dextran and oligosaccharide synthesis.

Dextransucrase (DSR-S) from Leuconostoc mesenteroides NRRL B-512F is a glucosyltransferase that catalyzes synthesis of soluble dextran from sucrose. In the presence of efficient acceptor molecules, such as maltose, the reaction pathway is shifted toward glucooligosaccharide synthesis. Like glucosyltransferases from oral streptococci, DSR-S possesses a C-terminal glucan-binding domain composed of a series of tandem repeats. In order to determine the role of the C-terminal region of DSR-S in dextran or oligosaccharide synthesis, four DSR-S genes with deletions at the 3' end were constructed. The results showed that the C-terminal region modulated the initial velocity of dextran synthesis but that the K(m) for sucrose, the optimum pH, and the activation energy were all unaffected by the deletions. The C-terminal domain modulated the rate of oligosaccharide synthesis whatever acceptor molecule was used (a good acceptor molecule such as maltose or a poor acceptor molecule such as fructose). The C-terminal domain seemed to play no role in the catalytic process in dextran and oligosaccharide synthesis. In fact, it seems that the role of the C-terminal domain of DSR-S may be to facilitate the translation of dextran and oligosaccharides from the catalytic site.

Amino Acid Sequence↗

LuxS-based signaling affects Streptococcus mutans biofilm formation.

Streptococcus mutans is implicated as a major etiological agent in human dental caries, and one of the important virulence properties of this organism is its ability to form biofilms (dental plaque) on tooth surfaces. We examined the role of autoinducer-2 (AI-2) on S. mutans biofilm formation by constructing a GS-5 luxS-null mutant. Biofilm formation by the luxS mutant in 0.5% sucrose defined medium was found to be markedly attenuated compared to the wild type. Scanning electron microscopy also revealed that biofilms of the luxS mutant formed larger clumps in sucrose medium compared to the parental strain. Therefore, the expression of glucosyltransferase genes was examined and the gtfB and gtfC genes, but not the gtfD gene, in the luxS mutant were upregulated in the mid-log growth phase. Furthermore, we developed a novel two-compartment system to monitor AI-2 production by oral streptococci and periodontopathic bacteria. The biofilm defect of the luxS mutant was complemented by strains of S. gordonii, S. sobrinus, and S. anginosus; however, it was not complemented by S. oralis, S. salivarius, or S. sanguinis. Biofilm formation by the luxS mutant was also complemented by Porphyromonas gingivalis 381 and Actinobacillus actinomycetemcomitans Y4 but not by a P. gingivalis luxS mutant. These results suggest that the regulation of the glucosyltransferase genes required for sucrose-dependent biofilm formation is regulated by AI-2. Furthermore, these results provide further confirmation of previous proposals that quorum sensing via AI-2 may play a significant role in oral biofilm formation.

Bacterial Proteins↗

Virulence of Streptococcus mutans: in vivo reversion of a low-virulence mutant results in partial displacement and pathogenesis.

A mutant of Streptococcus mutans 6715 wild type (WT), designated C4, has been shown previously to be defective in glucosyltransferase synthesis of insoluble glucan and to have low virulence in monoassociated gnotobiotic rats. The present investigation was concerned with the detection of WT-like variants of C4 in monoassociated rats, the supplantation of C4 by these WT-like organisms, and finally, the pathogenic potential of these WT-like organisms in gnotobiotic rats. In the first series of longitudinal studies with C4-monoassociated rats, WT-like organisms were detected at a low frequency (0.001%) in oral swab samples from only one of four cages of animals analyzed on day 7 after infection (age 27 days). The frequency of variants isolated from animals in the one cage increased, and by age 45 days these organisms represented approximately 1% of the mandibular plaque flora. After random redistribution of rats in the four cages (age 45 days), microbial analysis of oral swab samples (age 60 days) demonstrated the presence of variants in samples taken from rats in all four cages. The frequency of recoverable variants increased in older animals (age 90 days) and correlated with high caries activity. WT-like organisms were transmissible, since offspring (age 45 days) from these animals had high levels of variants as well as high caries activity. Similar results were obtained in a second longitudinal study; however, variants, although present in all four cages, were not detected until rats were 45 days old. All variant isolates exhibited morphological, biochemical, and in vivo virulence characteristics more similar to S. mutans 6715 WT than to C4. In vitro mixing experiments with C4 and either WT or a selected variant suggested that C4 was rapidly displaced by WT organisms. The results of this investigation demonstrate that the glucosyltransferase-defective, low-virulence C4 reverts to virulent WT-like organisms in vivo which compete more favorably for smooth surfaces than C4. Subsequently, these variants reached significant numbers in plaque which correlated with increased dental caries.

Animals↗

Physiology of "mutans-like" Streptococcus ferus from wild rats.

Strains of Streptococcus ferus isolated from the oral cavities of wild rodents inhabiting sucrose-rich and sucrose-poor environments have many traits in common with the "mutans" streptococci. Thus, S. ferus HD3 and 8S1, like cariogenic S. sobrinus 6715-13, from adherent, alpha (1 leads to 3) glucopyranosyl-glucose linkage-rich, plaquelike deposits in vitro and in vivo through the action of constitutive glucosyltransferase(s) enzymes on sucrose, produce and degrade intracellular polysaccharide, produce short-chain fatty acids from the catabolism of mono- and disaccharides, carry the c antigen of S. mutans, and penetrate, persist, and proliferate in a sucrose-augmented fashion in the oral cavities of specific-pathogen-free rodent caries models. However, unlike infection with common S. mutans, infection with tested S. ferus strains does not cause caries. This avirulence appeared to result more from the reduced aciduricity of S. ferus than from differences in glucosyltransferase complements. Studies showed that despite generally similar growth rates and extracellular glucan syntheses, the acidogenic metabolism of S. ferus was more inhibited by declining environmental pH than was cariogenic S. sobrinus 6715-13 and that, in vitro, less hydroxyapatite was solubilized by S. ferus metabolic end products. The physiology of these S. ferus strains demonstrated that, in addition to plaque formation and acid production, acid tolerance was crucial to the carious process.

Agglutination↗

Analysis of cell wall and membrane contamination of ribosomal preparations from Streptococcus mutans.

A ribosomal preparation from a cariogenic strain of Streptococcus mutans was examined for cell wall and membrane contamination. A biochemical characterization established that the preparation contained 61.0% RNA and 39.0% protein. Carbohydrate was not detected by phenol-sulfuric acid or methyl pentose assays. Glucosyltransferase and D-succinate dehydrogenase, which are cell wall- and membrane-associated enzymes, respectively, were not found. However, D-lactate dehydrogenase, another membrane-associated enzyme, was present in the preparation. A comparison of two-dimensional gel electropherograms of a mixture of cell walls and membranes and the S. mutans ribosomal preparation revealed contamination of the latter sample with at least six cell wall- or membrane-associated proteins. Adsorption of a rabbit antiserum raised against the ribosomal preparation with whole S. mutans cells abrogated antibodies directed against at least two proteins from the ribosomal preparation. Immunodiffusion plates showed reactivity of this antiserum against preparations of purified lipoteichoic acid from Streptococcus pyogenes and S. mutans. Adsorption of rat and rabbit antisera against the ribosomal preparation with the cell wall-derived materials glucosyltransferase, lipoteichoic acid, glucan, and a Rantz-Randall extract reduced the concentration of antibodies against the ribosomes by as much as 10-fold. These data indicated that the preparation was contaminated with at least six cell wall proteins, one cell membrane-associated enzyme, and lipoteichoic acid.

Bacterial Proteins↗