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At least 847 records · Page 47Linked to original sources
PubMed1996

[The characterization of Streptococcus mutans MT8148 and its glucosyltransferase deficient mutants].

The characterization of GTase-deficient mutants of S. mutans MT8148 was analysed to understand the possible virulence of GTase. In the presence of 1% sucrose, these mutants lost the ability to adhere to glass wall and the insoluble glucan synthesis was dramatically decreased. The GTase enzyme activity for insoluble glucan synthesis of these mutants was also decreased. Western blot using anti-CAGTase polyclonal antibody and anti-GTFI or anti-GTFSI monoclonal antibody showed the lack of the corresponding GTase which further confirmed the mutation of specific GTase gene.

Bacterial Adhesion↗
PubMed1967

The activity of uridine diphosphate glucose-d-fructose 6-phosphate 2-glucosyltransferase in leaves.

1. By using EDTA in reaction mixtures it was possible to determine the activity of sucrose phosphate synthetase in freshly prepared leaf extracts without the complications caused by sucrose phosphatase. 2. EDTA was found also to increase the activity of sucrose phosphate synthetase by as much as 100%. 3. High sucrose phosphate synthetase activities were found in leaf preparations in which sucrose phosphatase was inhibited by EDTA. By contrast with previous reports, the activities were sufficient to allow sucrose synthesis in leaves during photosynthesis to occur via sucrose phosphate. 4. Sugar-cane plants having different rates of photosynthesis also had different activities of sucrose phosphate synthetase in their leaves. 5. It is suggested that the activity of sucrose phosphate synthetase in leaves may play a role in the control of the rate of photosynthesis.

Journal Article↗
PubMed1971

Solubilization and Separation of Uridine Diphospho-d-glucose: beta-(1 --> 4) Glucan and Uridine Diphospho-d-glucose:beta-(1 --> 3) Glucan Glucosyltransferases from Coleoptiles of Avena sativa.

The particulate glucan synthetase preparation isolated from a homogenate of oat coleoptiles at 4 C lost 65% of its original activity after 1 day when the UDP-d-glucose substrate concentration was 5 x 10(-7)m to 1.0 x 10(-6)m. Storage of the particulate enzyme at -20 C or in liquid nitrogen did not prevent the enzyme from losing its activity. Incorporation of 0.5% hovine serum albumin into the medium stabilized the particulate enzyme at 0 C for 6 days and for at least 2 weeks in liquid nitrogen.When the particulate enzyme was treated with 8% digitonin, 40 to 50% of its activity appeared in the 100,000g supernatant fraction. The particulate and digitonin-solubilized enzyme preparations synthesized both beta-(1 --> 4) and beta-(1 --> 3) glucosyl linkages from UDP-d-glucose, but beta-(1 --> 3) glucan was the main product at 1 x 10(-3)m UDP-d-glucose substrate. The activity of beta-(1 --> 4) glucan synthetase was stimulated at least 10-fold in the presence of MgCl(2). A separation of beta-(1 --> 4) and beta-(1 --> 3) glucan synthetase activities could be achieved at 1 x 10(-3)m UDP-d-glucose when the digitonin-solubilized enzyme was adsorbed on a hydroxylapatite gel and then eluted with concentrated potassium phosphate buffer. The results indicate that the particulate enzyme contains two enzymes, one responsible for the synthesis of beta-(1 --> 4) and another beta-(1 --> 3) linkages in the glucan or glucans synthesized from UDP-d-glucose.

Journal Article↗
PubMed1971

Adenosine diphosphoglucose-starch glucosyltransferases from developing kernels of waxy maize.

TWO ADENOSINE DIPHOSPHOGLUCOSE: alpha-1,4-glucan alpha-4-glucosyl-transferases were extracted from kernels of waxy maize harvested 22 days after pollination and separated by gradient elution from a diethylaminoethyl-cellulose column. Both fractions could utilize amylopectin, amylose, glycogen, maltotriose and maltose as primers. The rate of glucose transfer from adenosine diphosphoglucose to rabbit liver glycogen of fraction II was 78% of the rate of glucose transfer to amylopectin, but with fraction I the rate of transfer of glucose to rabbit liver glycogen was 380% of that observed to amylopectin. Glucan synthesis in the absence of added primer was found in fraction I in the presence of 0.5 m sodium citrate and bovine serum albumin. The unprimed product was a methanol-precipitable glucan with principally alpha-1,4 linkages and some alpha-1,6 linkages, and its iodine spectrum was similar to that of amylopectin.

Journal Article↗
PubMed1974

Properties of glucosyltransferase and glucan transferase from spinach.

A glucosyl and a glucosyl-glucan transferase activity from spinach (Spinacia oleracea L. var. Matador) leaves have been partially purified and characterized. The latter activity (fraction 1 after diethylaminoethylcellulose chromatography) is responsible for the transfer of glucosyl as well as of maltosyl, maltotriosyl, and higher homologous residues to glucose giving rise to maltose and the correspondingly larger molecules. This fraction also shows beta-amylase activity. The transfer takes place only to glucose; maltose, as well as other alpha-1,4-glucans, serve as donors. The enzyme fraction 2 is amylase-free and catalyzes only the transfer of glucosyl moieties, again with high acceptor specificity to glucose. Maltose and larger alpha-1, 4-glucans, with the exception of maltotriose and maltotetraose, act as donors. The physiological function of these enzymes may be the formation of oligosaccharide primers for starch synthetase or phosphorylase.

Journal Article↗
PubMed1974

Partial Purification and Properties of a beta-d-Glucosyltransferase Occurring in Germinating Phaseolus aureus Seeds.

A soluble enzyme that transfers d-glucose from uridine diphosphate d-glucose to low molecular weight hydroxyl compounds has been discovered in germinating mung bean (Phaseolus aureus) seeds and purified 220-fold. Phenol and n-butyl alcohol are the most reactive aceptors examined. The reactivities of various acceptors are largely independant of hydroxyl group acidities or of the electronic properties of the acceptors. The space-filling properties or length of the acceptors, on the other hand, appear to be the predominant controlling factor which determines their relative abilities to accept d-glucose, the ideal size being that of phenol and n-butyl alcohol. The enzyme is deactivated by p-chloromercuribenzene sulfonate; dithiothreitol imparts considerable stabilization to the enzyme. It does not require exogenously added metal ions but is slightly stimulated by magnesium ion. On the other hand, the enzyme is partially inhibited by 10 mm manganous ion, cobalt ion, ferrous ion, and ethylenediaminetetraacetate. Zinc ion at 10 mm concentrations strongly inhibits the enzyme. The molecular weight of the enzyme, determined by gel filtration, is approximately 62,000.

Journal Article↗
PubMed1976

Membrane-bound UDP-Glucose: Lipid Glucosyltransferases from Peas.

An enzymic preparation from peas (Pisum satisum), able to form neutral and polar glycosides, is described. The best sugar donor is UDP-glucose and the acceptors are present in the enzymic system.The neutral glycolipids have been characterized as steryl and acylated steryl glucosides. The polar glucolipid had been identified as polyprenyl monophosphate glucose. The glucose is linked to the phosphate in beta configuration. Polar glucolipids are also formed from UDP-glucose and exogenous prenylic acceptors, either alpha-saturated, as dolichyl monophosphate, or allylic, as ficaprenyl monophosphate.THE TWO GLUCOSYLATING ACTIVITIES HAVE BEEN PARTIALLY SEPARATED BY DIFFERENTIAL CENTRIFUGATION: the fraction that precipitates at 25,000g has most of the neutral glucolipid-synthesizing activity, and the fraction that sediments at 100,000g is rich in polar glucolipid glucosyl transferase activity. This latter activity was strongly dependent on Mg(2+) concentration, the optimum being around 5 to 10 mm. UDP inhibits the reaction and 0.2 to 0.5% (v/v) Triton X-100 has a stimulatory effect. The optimum pH is 7.5.

Journal Article↗
PubMed1989

Zeatin Glycosylation Enzymes in Phaseolus: Isolation of O-Glucosyltransferase from P. lunatus and Comparison to O-Xylosyltransferase from P. vulgaris.

An enzyme catalyzing the formation of O-glucosylzeatin in immature embryos of Phaseolus lunatus was purified 2500-fold using ammonium sulfate precipitation followed by affinity and anion exchange chromatography. The enzyme uses trans-zeatin as substrate (K(m) 28 micromolar) but not cis-zeatin, ribosylzeatin, or dihydrozeatin. Both UDP-glucose and UDP-xylose can serve as glycosyl donors, with K(m)s of 0.2 and 2.7 millimolar, respectively, for the formation of O-glucosylzeatin and O-xylosylzeatin. In comparison, the UDPxylose-zeatin:O-xylosyltransferase (JE Turner, DWS Mok, MC Mok, G Shaw [1987] Proc Natl Acad Sci USA 84: 3714-3717) isolated by the same procedures from P. vulgaris embryos uses only UDP-xylose as donor substrate and the K(m)s for both zeatin and UDP-xylose are much lower (2 and 3 micromolar, respectively). The chromatographic behavior on affinity columns and molecular weights (approximate M(r) 44,000 daltons) of the two enzymes are similar. Results from substrate competition experiments and enzyme separation by anion exchange HPLC indicate a single, distinct, zeatin O-glycosylation enzyme occurs in embryos of each of these Phaseolus species.

Journal Article↗