Glycoproteins and Chitin

A homogeneous preparation of reduced and carboxymethylated )3-ovomucin has been shown to contain a subunit of molecular weight 1.12 x 10 , sulphate (4.24%), and carbohydrate (60%) consisting largely of D-galactose (22%), 2-amino-2-deoxy-D-galactose (8.9%), and sialic acid (10.6%). A soluble, fibrous component extracted from crude ovomucin with SM-guanidinium chloride contained 70% jS-ovomucin. 

A glycoprotein that comprises 77% dry-weight of grasshopper (Locusta migratorid) eggs has been found to contain D-mannose (14) and 2-amino-2-deoxy-D-glucose (2 residues per molecule), with the carbohydrate moiety linked to an asparagine residue.  

Hydroxyproline has been tentatively identified as the linkage residue in a number of apparently homogeneous proteoglycans obtained from rice bran.  

Exhaustive digestion of the jelly-coat of toad Bufo vulgaris) eggs with pronase yielded two glycopeptides containing different proportions of sialic acid.  

Three morphologically and functionally distinct layers of the jelly-coat of Zenopus laevis eggs have been shown to contain carbohydrate moieties linked 0-glycosidicalIy.  

A glycoprotein (mol. wt. 4.5x10 ) composed of carbohydrate (36%) and protein (53%) has been isolated from the articular lubricating fraction of bovine synovial fluid.It is likely that this glycoprotein is synthesized by the joint tissues and is not derived from serum. 

Crab chitin, and chitin from the diatom Thalassiorira fluviatilis dissolves in hexafluoro-2-propanol far-u.v. and c.d. spectra of solutions, gels, and films of the chitin have been recorded. A trans-amide conformation and intermolecu-lar hydrogen bonding are proposed as the important determinants of the observed solid state c.d. spectra. 

Chitins and chitosans from a variety of sources have simple e.s.r. spectra, provided they have been isolated and purified under controlled conditions to avoid excessive oxidative oxidation.The primary product of the thermal degradation of chitin, 2-acetamido-l,6-anhydro-2-deoxy-/3-D-glucopyranose, has been detected and isolated on a preparative scale.  

Chitin has been treated with isocyanate or acid chloride derivatives of pesticides to produce controlled-release polymeric pesticide systems.  

The action of lysozyme on partially deacetylated chitin and chitin oligosaccharides has been studied.Chitin was deacetylated to an extent of about 70% of its 2-acetamido-2-deoxy-D-glucosyl residues, and lysozyme digests of the deacetylated chitin were fractionated by gel chromatography, paper chromatography, and paper electrophoresis. 

One of the latest volumes in the series International Review of Science covers the isolation and structures of glycoproteins from ovarian cysts, gastric mucosa, submaxilliary glands, and erythrocytes. Physical and chemical data have been compiled for glycoproteins. Other reviews have discussed the chemistry, occurrence, and metabolism of sialic acids, with reference to cell-surface neuraminidases and the metabolism of molecules containing residues of sialic acid by cells transformed with tumourigenic viruses, and the effects of neuraminidases on intermolecular and intercellular forces.  

The amount of bound water (studied by H n.m.r. spectroscopy) and the extended molecular conformation appear to be responsible for the anti-freeze properties of a glycoprotein from the Antarctic fish Dissostichus mawsoni. Chemical modification has shown that the carbohydrate moiety of the glycoprotein component of the (Na + K )ATPase in membrane preparations of the salt glands from dog fish does not contribute to the catalytic activity of the enzyme. One of two glycoproteins extracted from squids (Sepia officinalis) resembles collagen.  

2- acetamido-2-deoxy-D-glucose, and 2-acetamido-2-deoxy-D-galactose, the carbohydrate component of Helix pomatia haemocyanin contains residues of 3-0-methyl-D-galactose and that from Lymnaea stagnalis haemocyanin contains residues of 

Proteins can be attached to Sephadex or Sepharose or cellulose by reaction with the oxidized polysaccharide (aqueous bromine at pH 7.0) and reduction of the resulting Schiff base with sodium cyanoborohydride. Cytochemical markers for detecting lectins bound to cell surfaces have been prepared by glycosylation of horseradish peroxidase and ferritin. 8-Methoxycarbonyloctyl glycosides have 

The chemistry, biochemistry, and industrial and medical uses of chitin have been reviewed. Partially de-JV-acetylated chitin, which was obtained following treatment of chitin with alkali at 25 °C for two or three days, was reasonably soluble in water at 0 The effect of sonic radiation on the morphology of microfibrils of chitins and celluloses has been correlated with the polarity of the constituent chains. For given conditions, fibrillation of the microfibrils takes place when the polarity of the chains is antiparallel but not when it is parallel. The synthesis of chitin by a wide variety of insect pests is inhibited by diflubenzuron (25).  

A review of complex carbohydrates, which includes a discussion of the structures, isolation, biosynthesis, and functions of glycoproteins, glycosaminoglycans, and blood-group substances, has appeared. The structures of the carbohydrate moieties found in glycoproteins from such diverse sources as fungal and mam-rhalian cells have been compared.  

Sharon, Complex Carbohydrates , Addison-Wesley, Reading, Mass., 1975. 

Aubert, G. Biserte, and M. H. Loucheux-Lefebvre, Arch. Biochem. Biophys., 1976,175, 410. 

Additional heterogeneity has been described amongst the asparaginyl-carbohydrates from ovalbumin. Digestion of fractions with exo-glycosidases is discussed in relation to the use of these glycopeptides for studies of glyco-syltransferase enzymes. 

The structures of glycopeptides I (59) and II from ovalbumin have been established. Glycopeptide II is now recognized as being composed of two glycopeptides, IIA (60) and IIB (61). 

The complete structures of the carbohydrate units of three other glycopeptides from ovalbumin (62—64) have been established, using a combination of sequential digestion with glycosidases. Smith degradation, selective acetolysis, and methylation analysis.  

Ovomucin has been separated into two fractions (A and B) having high and 

Dautigny, I. Bernier, J. Jollds, J. Colombani, and P. Joll, Comp, rend., 1977, 285D, 1535. 

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Renkema, G.H., Boot, R.G., Au, F.L., Donker-Koopman, W.E., Strijland, A., Muijsers, A.O., Hrebicek, M. and Aerts, J.M. (1998) Chitotriosidase, a chitinase, and the 39-kDa human cartilage glycoprotein, a chitin-binding lectin, are homologues of family 18 glycosyl hydrolases secreted by human macrophages. European Journal of Biochemistry 251, 504-509. 

Monosaccharides are constituents of such widely abundant biomolecules as starch, cellulose, pectin and chitin. They are units of the sugar chains of glycoproteins and other important glycoconjugates in bacteria and in eukaryotic... 

Figure 6.4 A. The Putative Structure of the Yeast Cell Wall. Disulphide bridges hold the mannan glycoprotein and glycan together. Chitin is confined to bud scars. B. The putative structure of the wall of a hyphal fungus. Septa differ slightly from hyphal walls in many species. The plasma membrane is indicated by M.

Glucosamine is an amino monosaccharide (amine sugar) that can be foimd in chitin, glycoproteins, and the glycosaminoglycans (mucopolysaccharides), such as heparin... 

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.

Monosaccharides may possess functionalities other than hydroxyls. Amino sugars are aldoses or ketoses which have a hydroxyl group replaced by an amino functionality. 2-Amino-2-deoxy-glucose is one of the most abundant amino sugars it is a constituent of the polysaccharide chitin. It also appears in mammalian glycoproteins, linking the sugar chain to the protein. Monosaccharides may also be substituted with sulfates and phosphates. Furthermore, deoxy functions can often be present, and important examples of this class of monosaccharides are L-fucose and L-rhamnose. 

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