Glucan, 5. cerevisiae cell wall

Investigation of a partially purified particulate gluean preparation from Saccharomyces cerevisiae cell walls has expanded. Glucan is held re-sponsil le for most of the reticuloendothelial-stimulating properties of zymosan. The preparation was reported to activate macrophages as assessed by... 

The preparations are featured with combining probiotics and prebiotics (mannans and glucans on cell walls of yeast Saccharomyces cerevisiae), and phytobiotics of the medicinal plants - Echinacea purpurea and holy thistle. Echinacea has immunomodulatory properties. Echinacea preparations exhibit antibacterial, antiviral and antifungal properties. When intaking the Echinacea preparations at metabolic disorders, at the impact of different chemical compounds of toxic nature, contained in the feed (heavy metals, pesticides, insecticides, fungicides), a stimulation of the immune system has been observed. 

Kapteyn, J. C., Montijn, R. C., Vink, E., De La Cruz, J., LlobeU, A., Douwes, J. E., Shlmof, H., Lipke, P. N. Kbs, F. M. (1996). Retention of Saccharomyces cerevisiae cell wall proteins through a phosphodiester-linked beta-l,3-/beta-l,6-glucan heteropolymer. Glycobiology, 6, 337-345. 

Intrinsic (natural, innate) resistance. In one form of intrinsic resistance, the fungal cell wall (see Chapter 2) is considered to present a barrier to exclude or, more likely, to reduce the penetration by biocide molecules. The evidence to date is sketchy but the available information tentatively links cell wall glucan, wall thickness and consequent relative porosity to the sensitivity of Saccharomyces cerevisiae to chlorhexidine. 

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)... 

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... 

Cell walls of Saccharomyces cerevisiae were found to contain a (1— 6)-linked j8-D-glucopyranan this was isolated, and identified by i.r. spectroscopy52 and chemical-analysis techniques.53 The alkali-in-soluble glucan from S. cerevisiae contains this and a (1— 3)-linked /3-d-glucopyranan in the ratio54 of 1 5.7. The former, of mol. wt. 2 x 105, has 6-0- and 3-O-substituted units in the ratio of 4.4 1, and contains 14% of 3,6-di-O-substituted units.55 (A similar heterogeneity occurred... 

The main structural constituents of Saccharomyces cerevisiae yeast cell wall are glucans and mannans with a minor proportion of chitin (Walker 1998). Manno-proteins are located in the outer layer of the yeast cell wall and determine most of the surface properties of the wall. Vasserot et al. (1997) studied the capacity of yeast lees to adsorb anthocyanins in an attempt to reduce the detrimental effects of charcoal on the color of red musts and wines. Experiments based on model wine solutions revealed that yeast lees possess a greater affinity for anthocyanins than... 

The cell wall of Saccharomyces cerevisiae has a structure of crossed molecules of /3-D-linked D-glucan, which gives the wall its strength and the cell its shape. This glucan is embedded in other polysaccharide(s) or in glycoprotein. Thus, yeast cell-walls consist mainly of polysaccharide, with relatively little protein, lipid, or min-... 

A historical review of the development of our knowledge of the yeast cell wall was given by Phaff (I). Most information based on chemical studies has been derived, by far, from studies with cell walls from baker s yeast, Saccharomyces cerevisiae, and closely related species. The principal components of Saccharomyces walls are several types of glucan and a mannan-protein complex which may contain variable proportions of phosphate. A low content of chitin (ca. 1% ) may be present depending on the number of times a cell has produced buds. The reason for this is that chitin is present only in the bud scars (ca. 3 pm2 in area) produced on the surface of a mother cell (2), each at a different place on the cell surface. 

Figure 1. Possible structures for alkali-insoluble ft-glucan from the cell wall of Saccharomyces cerevisiae after Manners et al. (3). Part A represents a comb-type structure, while part B represents a tree-type structure. In the former, most or all of the glucose residues comprising the backbone are thought to carry side chains with an average of ca. 30 glucose residues (two side chains shown). In the latter, a + b -f c comprise ca. 60 glucose residues. See text for further details.

Cell-wall formation in Saccharomyces cerevisiae appears to be the result of two main patterns of deposition of wall material, viz., around the whole periphery of the non-budding cells and mainly at the tip of the daughter cell, or at the cross-wall that separates dividing cells. Synthesis and secretion of j3-D-glucan is unaffected by inhibition of RNA and protein synthesis. Growth of S. cerevisiae under conditions of phosphate limitations results in a decreased content of D-glucan and increased protein content as compared with control cells. 

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