Fungi chitin

In the more abundant a chitin the chains in alternate sheets have opposite orientations, possibly a result of hairpin folds in the strands. Native chitin exists as microfibrils of 7.25 nm diameter. These contain a 2.8-nm core consisting of 15-30 chitin chains surrounded by a sheath of 27-kDa protein subunits. The microfibrils pack in a hexagonal array, but the structure is not completely regular. Several proteins are present some of the glucosamine units of the polysaccharide are not acetylated and the chitin core is often calcified. The commercial product chitosan is a product of alkaline deacetylation of chitin but it also occurs naturally in some fungi. Chitin is also present in cell walls of yeasts and other fungi. It is covalently bonded to a P-l,3-linked glycan which may, in turn, be linked to a mannoprotein (see Section D,2). ... 

Plant and animal remains, representing the main types of carbon compounds added to the soil, contain the carbon included in high-molecular weight compounds. In plants the main types of these are cellulose, hemi-cellulose and lignin, followed by smaller quantities of fats, waxes and oils, proteins and nucleic acids. In invertebrates and fungi chitin occurs, whereas in bacteria it is peptidoglycan (murein). 

D-linear Crab and lobster shells, fungi Chitin... 

Chitin is undoubtedly the most abundant animal polysaccharide on earth. It constitutes the basic element of the exo-skeleton of insects and crustaceans, but it is also found in the outer skin of fungi. Chitin is a regular linear polymer whose structure differs from that of cellulose by the presence of Al-methylamide moieties instead of the hydroxyl groups at C2 (Fig. 1.17). Given the susceptibility of this function to hydrolysis, chitin often bears a small fraction of monomer units in the form of primary amino groups resulting from that chemical modification. 

Momilactones arise from GGPP via 9,pH-labdadienyl pyrophosphate (66) and 9-3H-pimara-7,15-diene (67), whereas oryzalexins arise via copalyl pyrophosphate (35) and sandaracopimaridiene (36). Both groups of diterpenes appear to be synthesized in the cytosol. Only kaurene is found in tissue not attacked by fungi. Chitin proved to be the best elicitor of momilactones in cell culture (West et al., 1990). Chitinase probably breaks down the chitin to active fragments (West et al., 1990). Both types of phytoalexins from rice are probably important in disease resistance, but the relative importance of each has not been assessed (West et al., 1990). 

Chitin is a polysaccharide found in the outer skeleton of crustaceans, insects, crabs, shrimp, lobsters, in the internal structures of other invertebrates, and in the ceU walls of fungi. Chitin (poly-N-acetyl-d-glucosamine, 2-acetamido-2-deoxy-l,4-P-d-glucan) (Figure 11.6) is one of the three most abundant polysaccharides in nature, is biodegradable, non-toxic, and readily biocompatible. 

Schizomycophyta Myxomycopkyta EumycophyUt (bacteria, molds, and fungi) chitin cellulose mannans starches levans glycogen extracellular polysaccharides... 

These appear to contain a cell wall substance which was detected in Endo-myces and Penicillium notatum in emphasis of the close relationship between Schizosaccharotnyces and the hyphal fungi. Chitin does, however, occur in Penicillium notatum. No detailed structural work has been done on fungal chitin but its close resemblance to crustacean chitin suggests that it is a poly-2-iV-acetamide-2-deoxy-D-glucosan linked /3-(i ->4)-glycosidically in linear chains. 

A number of important papers could not be cited in this chapter, due to the length limitations and the specific target of the chapter. For example, the antimicrobial activity of chitosans [349], the chitinolytic enzymes, the preparation of cosmetics, and the occurrence of chitin in fungi [350] are some of the subjects not dealt with specifically here, notwithstanding their importance. 

It may be that this fact was associated with the rather complex composition of fungal mycelium, consisting of chitin enclosed in a glucan matrix (Bowman, Free, 2006). Therefore, mature saprophyte mycelium are completely covered by difficult-soluble glucans and the fraction of chitin in the apical cell wall is not sufficient. As such, we supposed that these cationic isoforms bound with another major component of the fungi... 

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