D-Glucans synthesis

The enzymes involved are nucleoside diphosphohexosetransferases, probably GDP-D-mannosyltransferase (EC 2.4.1.32) and UDP-D-galactosyl-transferase. For a structurally related polymer, (1 - 6)-a-D-xylosyl-(l - 4)-/3-D-glucan, synthesis was shown to involve concurrent incorporation of D-xylose and D-glucose, and not substitution by D-xylose of a preformed (1 - 4)-/3-D-glucan chain.34 The insolubility of (1 - 4)-/3-D-glucan and man-nan would make the latter mechanism unlikely. 

Results of later studies by Delmer and coworkers189,179 provided some support for this hypothesis. Thus, it was shown that re-establishment of a transmembrane, electrical potential (positive-inside) across vesicles isolated from cotton fibers resulted in a 4-12-fold stimulation of /3-D-glucan synthesis from UDP-glucose (see Fig. 5). Such a potential was established by the addition of K+ in the presence of an imper-... 

Sivak. M. N., 1992. (1— 4)-a-D-Glucan synthesis by a chloroplastic phosphorylase isolated from spinach leaves is independent of added primer. Carbohyd. Res. 227, 241-255. 

Papulacandin B, an antibiotic produced by the deuteromycete Papularia sphaerosperma, inhibits the growth of yeasts, but has no effect on other fungi, bacteria, or protozoa.The mode of action involves the inhibition of synthesis of alkali-insoluble jS-D-glucan of Saccharomyces cerevisiae and Candida albicans in sphaeroplasts and causes lysis of cells by osmotic rupture.Echinocandin B and a structurally related antibiotic aculeacin A also inhibit j3-D-glucan synthesis in yeast, possibly in a similar manner.Papulacandin B has been shown to inhibit the transfer of D-glucose from UDP-D-glucose, but not D-mannose from GDP-D-mannose, into dolichyl phosphate. 

In a model experiment, glucoamylase (ex Rhizopus niveus) was shown to inhibit a-D-glucan synthesis as catalysed by potato phosphorylase (see p. 498).29 ... 

The interactions between cell-free D-glucosyltransferase of S. mutans (serotype d) and water-insduble and water-soluble ( D-glucans of different origin have been reported. The effects of these interactions on de novo o-D-glucan synthesis and adherence to glass surfaces has been considered. 

Echinocandins (i.e. caspofungin), semisynthetic lipo-peptides, inhibits the synthesis of (3-(l,3)-D-glucan, an... 

The synthesis of linear 4 —> 1-a-D-glucans from D-glucopyranosyl phosphate by the action of phosphorylases has been shown by comparison of results of methylation and end-group assay and viscosity determination,209 and by potentiometric, iodine titrations82 on the product. The chain length of the enzymic product (100 to 200 D-glucose units) is less than that of the natural component. Whether this is due to impure enzymes cannot yet... 

Pharmacology Micafungin is a semisynthetic lipopeptide (echinocandin) synthesized by a chemical modification of a fermentation product of Coleophoma empetri F-11899. Micafungin inhibits the synthesis of 1,3- -D-glucan, an essential component of fungal cell walls, which is not present in mammalian cells. Pharmacokinetics ... 

Mechanism of Action Inhibits the synthesis of (beta) (1,3)-D-glucan, an integral component of fungus cell wall... 

With respect to the first of these hypotheses, auxin enhances the rate of wall synthesis in virtually every tissue in which growth is also promoted.482,483 It seems certain that this stimulation extends to all components of the wall polysaccharide6,484 and to wall glycoprotein.485,486 Auxin has been shown to stimulate / -D-glucan synthetase activity in several plant-tissues.7,487... 

The situation is complicated by the fact that the efficiency of cellulose synthesis in the cell-free system is low, and the same enzyme preparation catalyzes the incorporation of D-glucosyl groups from UDP-Glc into alkali-soluble (1 - 2)-/3-D-glucans.370 A similar process was reported to occur with a membrane preparation of Rhizobium meliloti,371... 

N. K. Kochetkov, N. N. Malysheva, E. M. Klimov, and A. V. Demchenko, Synthesis of polysaccharides with 1,2-c -glycosidic linkages by tritylthiocyanate polycondensation. Stereoregular a-(l-6)-D-glucan, Tetrahedron Lett., 33 (1992) 381-384. 

The phytoalexin elicitor (PE) family of /1-D-glucans (Fig. 5) was selected as a target because these oligosaccharides had been synthesized previously in solution48,49 and on the solid support.50,51 It was our intention to investigate not only the application of glycosyl phosphates to automated solid-phase synthesis, but also to compare our method to the previously described reports of PE syntheses. 

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