Cell wall fractions

In maize-root tips, high specific activities of/ -D-galactosidase, a- and jff-D-glucosidase, N-acetyl-/ -D-glucosaminidase, acid phosphatase, and phosphodiesterase (EC 3.1.4.1) are found in the cell-wall fraction.246... 

All of the enzymes responsible for formation of cell-wall polysaccharide appear to be membrane-bound, and are usually recovered in the particulate, cell-wall fraction sedimenting at 20,000g none have been purified significantly. Several names have been given to these complex enzyme-systems, which may possess more than one activity, including polysaccharide synthase and glycosyltransferase. The term polysaccharide synthase is preferred for use in this article. 

Two cell-wall fractions were obtained from mycelia of Neurospora crassa by differential extraction with alkali (soluble in 4%, and insoluble in 24%) on incubation with endo-(l - 3)-/3-D-glucanase, both gave473 D-glucose, laminara-biose and -triose, and 62-/3-D-glucosyllaminarabiose (118). exo-(1 - 3)-/3-D-Glucanase released D-glucose and gentiobiose. Structures were proposed for both fractions when this evidence and the results of methylation analysis were considered. 

The authors usually freeze-dry samples for convenience and analyze later with the cell walls and cell-wall fractions. 

Several procedures have been used to hydrolyze polysaccharides in cell walls and cell wall fractions. For example, the noncellulosic polysaccharides can be hydrolyzed using 1 M sulfuric acid for 2 to 3 hr at 100°C (Selvendran and Ryden, 1990). One of the simplest procedures is that of Albersheim et al. (1967) in which hydrolysis of the noncellulosic polysaccharides is achieved by incubating in 2 M trifluoroacetic acid (TFA) at 121 °C for 1 hr. The advantage of the TFA procedure is that it is quick and the acid can be removed by evaporation in a gentle stream of air or nitrogen. However, neither the 1 M sulfuric acid or TFA procedures hydrolyze cellulose. Hydrolysis of cellulose can be achieved by an initial dispersion in 72% (w/w) sulfuric acid (Saeman et al., 1963 Selvendran et al., 1979 Fry, 1988 Harris et al., 1988 Selvendran and Ryden, 1990) followed by hydrolysis in 1 M sulfuric acid. 

Dried cell walls or cell-wall fractions (unitfj.i)... 

Place 5 mg of dried cell walls or cell-wall fractions (uNrr E3.i) into a scrupulously clean (see Critical Parameters) borosilicate glass tube (in duplicate). Record the exact weight of cell walls or fractions. 

Cell walls and cell wall fractions are first hydrolyzed using the method of Ahmed and Labavitch (1977) and the uronic acid content estimated using the method of Filisetti-Cozzi and Carpita (1991). 

Weigh 5 mg (record exact weight) of cell walls or cell-wall fraction (in duplicate) into borosilicate glass tubes (see unit E3.i for cell wall preparation and cell-wall fractionation). 

Plane-polarized radiation, CD analysis of proteins, 219-243. see also Circular dichroism Plant cell walls fractionation... 

Listeria monocytogenes Pathogen Cell wall fractionation label-free SRM Cell wall proteome and associated functions (183-185)... 

The variety of aldehyde oxidases discovered in other plants have similarities to the maize enzyme, but also have some very important differences. Enzymes contained in a cell wall fraction from barley seedlings were able to oxidize IAAld to form IAA at a pH optimum of 7 and Km of 5 pmol 1 1, which was very similar to the enzyme found in maize.113 Two aldehyde oxidases from potato have also been identified 101 they had a similar pH optimum (between 7 and 8), but preferred aliphatic aldehydes to aromatic aldehydes. Although oat and cucumber aldehyde oxidases have been shown to oxidize IAAld to produce IAA,102 114 the oat enzyme had a lower pH optimum and higher Km than the maize enzyme, and the cucumber enzyme was inhibited by synthetic auxin and activated by 2-mercaptoethanol, which was not true for the maize enzyme. The difference in the enzymes makes it difficult to envision a common evolutionary origin for the IAAld pathway in plants if these particular enzymes are involved in each case. 

E. Deniaud, J. Fleurence, and M. Lahaye, Preparation and chemical characterization of cell wall fractions enriched in structural proteins from Palmaria palmata (Rhodophyta), Bot. Mar., 46 (2003) 366-377. 

Escherichia coli (B) cell-wall fraction h-glycero-o-manno- — 32... 

Nunez, Y.P, Carrascosa, A.V., Gonzalez, R., Polo, M.C., and Martfnez-Rodriguez, A. (2006). Isolation and characterization of a thermally extracted yeast cell wall fraction potentially useful for improving the foaming properties of sparkling wine. J. Agric. Food Chem., 54, 7898-7903. 

The presence of 0.3% of phosphorus in bakers yeast cell-wall mannan was observed by Northcote and Horne. " Phosphorus is associated with other mannan-containing, cell-wall fractions. The degree of phosphorylation varies from 1 phosphate group i>er 19 D-mannopyranosyl residues to 1 in 13. Partial hydrolysis gave a mannose 6-phosphate, and it appears that the phosphate group in the cell wall contains a second, more acid-labile, ester linkage (see Section IV, 2, p. 395). 

Brewers and bakers dried yeasts are used as dietary supplements. They contribute some protein and trace minerals, and some B vitamins, but no vitamin C, vitamin B 2 or fat-soluble vitamins. The glucose tolerance factor (GTE) of yeast, chromium nicotinate, mediates the effect of insulin. It seems to be important for older persons who cannot synthesize GTF from inoiganic dietary chromium. The cell wall fraction of bakers yeast reduces cholesterol levels in rats fed a hypercholesteremic diet. 

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