Amino polysaccharide components

Tryptophan 108 is recognized to be an active site in promoting the hydrolysis of 3(l,4)-glycosidic linkages between amino sugar residues in polysaccharide components of the bacterial cell walls. This residue is shown to occupy the cleft as well as trjrptophan 62 and 63, and is in a hydrophobic region. Tryptophan residues 62 and 108 are indispensable for the action of lysozyme, and tryptophan 62 is known to be the only binding site for the complex formation (13). Oxidation of tryptophan-108 is expected... 

The sensitivities of these methods are related to the amino acid compositions of the standard and unknown proteins, among other factors including the exposure of particular residues, which affects their reactivities. In addition, glycoproteins often react differently with the assay reagents than do proteins lacking a polysaccharide component. Therefore, when calibration curves are made using different standard proteins, their slopes are different. The choice of a standard protein will determine whether total protein is over- or underestimated in the unknown sample. 

Many complex polysaccharides contain modified sugars that are covalently linked to various small groups, particularly amino, sulfate, and acetyl groups. Such modifications are abundant in glycosaminoglycans, major polysaccharide components of the extracellular matrix that we describe In Chapter 6. 

The polysaccharide component of the serologically active lipopolysaccharide from Yersinia pseudotuberculosis is composed of residues of 3-deoxy-2-octulo-sonate, l- and Ti-glycero-v>-manno-h pios, D-mannose, D-glucose, paratose, L-fucose, D-galactose, and 2-amino-2-deoxy-D-glucose. The type-specific,... 

Biopolymers are the naturally occurring macromolecular materials that are the components of all living systems. There are three principal categories of biopolymers, each of which is the topic of a separate article in the Eniyclopedia proteins (qv) nucleic acids (qv) and polysaccharides (see Carbohydrates Microbial polysaccharides). Biopolymers are formed through condensation of monomeric units ie, the corresponding monomers are amino acids (qv), nucleotides, and monosaccharides, for proteins, nucleic acids, and polysaccharides, respectively. The term biopolymers is also used to describe synthetic polymers prepared from the same or similar monomer units as are the natural molecules. 

In tandem with his studies of polysaccharides, Stacey had a research group investigating the chemistry of the unusual sugars found as components of carbohydrate macromolecules. In this context, derivatives of simple sugars, di- and trisaccharides, uronic acids, deoxy sugars, amino sugars, sugar sulfates, and phosphates were studied. 

Six 2-amino-2,6-dideoxyhexoses are known as components of bacterial polysaccharides, namely, those having the d- and h-gluco, i.-manno, d- and L-galacto, and L-talo configurations. 2-Amino-2,6-dideoxy-D-glucose (d-quinovosamine) occurs in some LPS for example, that from Pseudomonas... 

The first known 1-carboxyethyl ether of a sugar was 2-amino-3-0-[(/ )-l-carboxyethyl]-2-deoxy-D-glucose or muramic acid (37). It is a component of the polysaccharide moiety of the peptidoglycan in the bacterial cell-wall. It is partially replaced by the mamo isomer, 2-amino-3-6>-[(/ )-l-carboxy-ethyl]-2-deoxy-D-mannose, in the peptidoglycan from Micrococcus lyso-deikticus. 

Proteins, the main constituents of the animals body, are polypeptides, biopolymers consisting of many amino acid molecules (the monomers) combined together (see Chapter 11) collagen, for example, the main component of animal skin, is a complex protein consisting of many molecules of amino acids combined together into polypeptide chains (see Fig. 71). Polysaccharides, the essential constituents of plants, also consist of many monosaccharide molecules combined together. Cellulose, the most abundant biological material on earth, which makes up most of the structural... 

The purification of a pneumococcal polysaccharide may be difficult, and the polysaccharide material is sometimes contaminated by a cell-wall component known as the C-substance. The methods for structural analysis of polysaccharides (which, like several of the pneumococcal polysaccharides, contain amino sugar and uronic acid... 

The difficulties inherent in obtaining correct sugar analyses for a polysaccharide containing three different amino sugars are obvious. It therefore seems possible that S4 is composed of tetrasaccharide repeating-units, containing one residue each of the four different sugar components. 

Figure 22.11. Cellulose is a structural and rather chemically inert component of terrestrial plants. Alginic acid is synthesized by marine algae and has medicinal properties. Some polysaccharides contain nitrogen in the form of amino sugars. The primary example of this is chitin, which composes the exoskeletons of Crustacea. An amino sugar contains an amine in place of a hydroxyl group. In other polysaccharides, sugars combine with lipids and proteins. These form glycoUpids and glycoproteins, respectively.

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