Non-cariogenicity of the disaccharide palatinose in experimental dental caries of rats.
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The caries-inducing activity of palatinose (isomaltulose, alpha-D-glucopyranosyl-1,6-fructose) was examined in in vitro and in vivo experiments, comparing it with other carbohydrates. When Streptococcus mutans was successively subcultured in a broth medium containing 1% palatinose, the strains belonging to serotype a, d, or g did not ferment palatinose, whereas the strains belonging to serotype b, c, e, or f did ferment palatinose. Furthermore, palatinose significantly inhibited the synthesis of insoluble glucan from sucrose by S. mutans. Specific-pathogen-free rats which had been infected with S. mutans 6715 and fed a diet containing 56% palatinose did not develop significant dental caries. However, rats infected similarly, but fed a diet containing sucrose, glucose, fructose, or a glucose-fructose mixture manifested significant caries when compared with the noninfected, sucrose-fed control rats. Furthermore, it was found that replacement of half of the sucrose content with palatinose resulted in decreased caries development compared with caries development in rats fed the sucrose diet. (+info)
Enzymically produced cyclic alpha-1,3-linked and alpha-1,6-linked oligosaccharides of D-glucose.
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A new type of bacterial enzyme hydrolyzed alternan (Leuconostoc mesenteroides NRRL B-1355 fraction S dextran, an alternating alpha-1,3-alpha-1,6-D-glucan) to give rise to a series of oligosaccharides. The oligosaccharide formed in the greatest proportion was a cyclic tetrasaccharide of D-glucosyl residues linked in an alternating alpha-1,3-alpha-1,6 fashion. Other saccharide products included isomaltose and alpha-D-glucopyranosyl-1,3-alpha-D-glucopyranosyl-1,6-D-glucose. Oligosaccharides of higher degrees of polymerization were also formed, and included alpha-D-glucosylated derivatives of the cyclic tetrasaccharide. This is the first report of a naturally produced cyclic tetrasaccharide. (+info)
Molecular cloning and expression of an isomalto-dextranase gene from Arthrobacter globiformis T6.
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The gene encoding an extracellular isomalto-dextranase, designated imd, was isolated from the chromosomal DNA of Arthrobacter globiformis T6 and cloned and expressed in Escherichia coli. A single open reading frame consisting of 1,926 base pairs that encoded a polypeptide composed of a signal peptide of 39 amino acids and a mature protein of 602 amino acids (M(r), 65,900) was found. The primary structure had no significant homology with the structures of any other reported carbohydrases, including two other dextranases. Transformed E. coli cells carrying the 2.3-kb fragment overproduced isomalto-dextranase into the periplasmic space under control of the promoter of the imd gene itself. (+info)
Isomalto-oligosaccharide-containing lipoteichoic acid of Streptococcus sanguis. Basic structure.
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The lipoteichoic acid of Streptococcus sanguis DSM 20567 and of DSM 20068 was isolated by phenol/water extraction and hydrophobic-interaction chromatography. The preparations from both strains have an identical structure: a 1,3-linked poly(glycerophosphate) chain phosphodiester-linked to Glc-(alpha 1-2)Glc(alpha 1-3)acyl2Gro as the lipid anchor. The chain is substituted with D-alanine ester and glycosyl residues which comprise mono-, di-, tri- and tetra-alpha-D-glucopyranosyl residues with (1-6) interglycosidic linkages. The glycosylglycerols were released with 48% (by mass) hydrofluoric acid, separated and characterized by a combination of chemical procedures and modern techniques of 1H-NMR and 13C-NMR spectroscopy. The alpha-isomalto-oligosaccharides add a novel motif to lipoteichoic-acid chain substituents. 1H-NMR and 13C-NMR spectroscopy also provided a detailed picture of the basic glycosylated poly(1,3-glycerophosphate) diglucosylglycerol. It proved a single unbranched chain structure, provided evidence for the chain length, the extent of glycosylation, the structure of the lipid anchor and the site of attachment of the poly(glycerophosphate) chain on the lipid anchor. Owing to its unique glycosyl substituents the lipoteichoic acid may serve as a taxonomic marker for the redefined species S. sanguis (formerly S. sanguis type I). (+info)
Isomalto-oligosaccharide-containing lipoteichoic acid of Streptococcus sanguis. Microheterogeneity and distribution of chain substituents.
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The lipoteichoic acid of Streptococcus sanguis DSM 20567 contains a poly(glycerophosphate) chain, with 49% of the glycerophosphate residues being substituted with D-alanine ester, 35% with alpha-D-glucopyranosyl and alpha-isomalto-oligosaccharide residues. Analysis of molecular species by affinity chromatography on concanavalin A showed all chains to be substituted and alanine ester and glycosyl residues to be present on the same rather than on separate chains. Molecular species varied in the length of the poly(glycerophosphate) chain, the extent of glycosylation, and had a constant alanine-ester content. An alkali-hydrolysis procedure revealed a distribution pattern between random and regular for the glycosyl substituents and suggested a similar distribution for the alanyl residues which occupy the free positions between the glycosyl substituents. (+info)
Bacillus thermoamyloliquefaciens KP1071 alpha-glucosidase II is a thermostable M(r) 540,000 homohexameric alpha-glucosidase with both exo-alpha-1,4-glucosidase and oligo-1,6-glucosidase activities.
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alpha-Glucosidase II of the facultative thermophile Bacillus thermoamyloliquefaciens KP1071 (FERM-P8477; growth over 30-66 degrees C) was purified to a homogeneous state. Its M(r) was estimated as 90000 by SDS/PAGE. However, the enzyme behaved as an active Mr 540000 protein on gel filtration with each of two gels of different matrices as well as on gel electrophoresis under native conditions. The enzyme was not glycosylated. Its isoelectric point was estimated as 5.7. The N-terminal sequence of 20 residues was determined asAla1-Ile-Gln-Pro-Glu-Gln-Asp-Asp-Lys-Thr-Gln-Glu-Asp-Gly- Tyr-Ile-Asp-Ile-Gly-Asn20. The sequence did not resemble those of procaryotic and eucaryotic proteins hitherto reported including the monomeric exo-alpha-1,4-glucosidase and the monomeric oligo-1,6-glucosidase from the same microorganism. The alpha-glucosidase II had no antigenic group shared with the latter two enzymes. Analysis of substrate specificity showed that the alpha-glucosidase II has dual activity towards oligo-1,6-glucosidases and exo-alpha-1,4-glucosidases, but its preference is for non-reducing terminal alpha-1,4 glucosidic bonds in substrates. Kinetic studies proved that both activities are attributed to the same catalytic site. The enzyme was most active at 81 degrees C and pH 7.0. Its half-life at pH 6.8 was 10 min at 81 degrees C, and 5 h at 55 degrees C in 6.4 M urea, 26% ethanol or 2.5% SDS. We suggest that the alpha-glucosidase II is a thermostable, homohexameric enzyme of origin distinct from the exo-alpha-1,4-glucosidase and the oligo-1,6-glucosidase present in the same strain. (+info)
Total intestinal lactase and sucrase activities are reduced in aged rats.
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Lactase-phlorizin hydrolase (LPH) and sucrase-isomaltase (SI) are intestinal microvillus membrane hydrolases that play important roles in carbohydrate digestion. Although the expression of these enzymes during postnatal development has been characterized, the effect of old age on disaccharidase activity is poorly understood. In the present investigation, we examined the effect of aging on lactase and sucrase activities and their mRNA levels in the small intestines of 3-, 12- and 24- mo-old rats by sampling from nine equidistant segments of small intestine. Total intestinal disaccharidase activity or mRNA abundance was determined from areas under the proximal-to-distal curves. Rats 24 mo of age had total intestinal lactase and sucrase activities that were 12 and 38% lower, respectively, than the 3-mo-old animals (P < 0.05). In contrast, total LPH and SI mRNA abundance did not change significantly. Thus, total intestinal lactase and sucrase activities decrease with age in a manner that likely involves a posttranscriptional process. The age-related decline in disaccharidase activity, if extrapolated to humans, may have important implications for the digestion of carbohydrate contained in the diet of the elderly. (+info)
Effects of a hydrogenated isomaltooligosaccharide mixture on glucan synthesis and on caries development in rats.
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The caries inhibitory effect of the hydrogenated derivative of an isomaltooligosaccharides mixture (IMO-H) was examined in vitro and in vivo experiments. IMO-H could not be used as a substrate for the crude glucosyltransferases (GTases) of Streptococcus sobrinus 6715 to synthesize water-insoluble glucan. Moreover, it not only significantly inhibited the synthesis of water-insoluble glucan from sucrose, but also the sucrose-dependent adherence of these growing cells the glass surfaces. In the in vivo experiment, the addition of IMO-H to a sucrose-containing diet resulted in significant reduction of caries development in specific-pathogen-free (SPF) rats infected with S. sobrinus 6715. (+info)