The Glucans

Single linkage type. Several of these are neutral glucans, eg curdlan. Others are polyanionic homopolymers and, unlike the glucans, also contain acyl groups. 

The glucan synthase inhibitor caspofungin (intravenous formulation) is new on the market for the treatment of invasive aspergillosis in patients whose disease is refractory to, or who are intolerant of, other therapies. During the clinical trials fever, infused vein complications, nausea, vomiting and in combination with cyclosporin mild transient hepatic side effects were observed. Interaction with tacrolismius and with potential inducer or mixed inducer/inhibitors of drug clearance was also seen. 

If branching is (1 —> 3), no glycol grouping will be present in any central unit and it may be seen that reaction will only occur on the terminal units. Such is the case with the polysaccharide laminarin, with the glucan of yeast membrane, and with a galactose-containing polysaccharide isolated from agar.146-148... 

The cell wall of S. cerevisiae is composed of glucan, mannoproteins, and chitin (Klis, 1994 Cid et al., 1995). Of the mannoproteins, some of them are first synthesized as GPI-anchored and mannosylated proteins. Subsequently, they are incorporated from the plasma membrane to the cell wall and are covalently linked to the glucan there. Therefore, some signals should exist for dictating the cell wall incorporation. One found at a short N-terminal region near the GPI-attached asparagine (the co-site) is important (Hamada et al., 1998b). Namely, a plasma membrane GPI-anchored protein was localized to the cell wall if the (V/I)... 

Glucansucrases are elaborated by Lactobacilli (Leuconostoc and Streptococcus species) and catalyze the synthesis of glucans from sucrose. In 1954, Jeanes et al. (1) surveyed 96 L. mesenteroides species that produce glucans from sucrose and found that the glucans... 

Fig. 2 Mechanisms proposed for the pol3no[ierization of glucans by glucansucrases by addition of glucose to the reducing end of the glucan chain.

Deoxymulundo-candin (158) Echinocandin- type antifungal antibiotic Aminocandin (NXL-201, IP960, HMR-3270)(159) Antifungal (Candida sp. infections) Targets the glucan in fungal cell walls Phase I Novexel 825-827... 

Functionally, starch can be considered as a polysaccharide synthesized in a manner permitting its efficient degradation. Hence, biosynthesis of the starch granule is a delicate balance between efficient packing of the glucan chains and the possibility of breaking these structures at degradation. To complete this enzymatically catalyzed process in the potato tuber, a multitude of different enzyme activities are required. 

A / -D-glucan has been isolated from the cell walls of 3-day-old, mung-bean hypocotyls.76 Extracts of cell walls of older hypocotyls were deficient in this polysaccharide. The glucan contained 3-linked and 4-linked glucopyranosyl residues in the molar ratio of 1.0 1.7. However, the hypocotyl tissue from which the glucan was extracted contained both primary and secondary walls, and therefore, the polymer cannot be definitely characterized as a primary cell-wall component. 

A number of dextrans have been examined with a pig-spleen a-D-glucosidase.437 This enzyme could differentiate exterior a-(l - 2) linkages, because it readily hydrolyzed a-(l - 3) and a-(l - 6), but more slowly split a-(l- 2), linkages in the glucans. 

The cell-wall j3-D-glucan fractions, insoluble in alkali and acid, from wild and from a mutant S. cerevisiae have been compared. Methylation analysis indicated more 1,3- and 1,3,6-linked D-glucosyl residues, and fewer 1,6-linked in the latter. The wild type was hydrolyzed less by exo-(l- 3)-/3-D-glucanase and more by endo-(l -> 6)-/3-D-glucanase than was the glucan from the mutant, consistent with the methylation data.4733... 

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