糖蛋白（glycoprotein）.docVIP

糖蛋白（glycoprotein） glycoprotein Macromolecules that are found in organisms and are formed by covalent binding of peptide chains and sugar chains. Usually a chain, in some amino acid residues of the polypeptide chain, combined with a sugar chain or long or short, the binding sites for serine or threonine hydroxyl (O- glycosidic bond also is amido), asparagine (N- glycosidic bond). Glycoproteins and two other proteins that are covalently bound together with proteins and sugars - proteoglycan and peptidoglycan - differ in structure and molecular weight range. Proteoglycans are found mainly in connective tissue of animals, and their molecular weight is usually between 106 and 108. The carbohydrate chains are mostly repeated by two monosaccharide units consisting of two monosaccharides. Peptidoglycan is found in the cell walls of prokaryotes and consists of large molecules of alternating sugars and amino acids. Glycoproteins are found in various organisms and in all types of tissue cells. Glycoproteins are estimated to account for more than 1/2 of all natural proteins. Among the various proteins in human serum, 50% are glycoproteins; more than 95% of all proteins in egg white are glycoproteins. Glycoproteins are present on all cell surfaces. There are more glycoproteins in the secretions and body fluids of animals and plants. Glycoproteins have a wide range of biological activities. More adequate evidence of lubrication, transportation, identification, protection and other functions. Generally, there is a peptide chain in a glycoprotein molecule. The number of sugar chains is small, one to many, and the other to hundreds. The proportion of sugar components to total molecular weight, or less than 1%, such as collagen, or more than 80%, such as: blood group substances. The composition of a peptide chain in a glycoprotein molecule, similar to that of a common protein, and sometimes higher in serine and threonine content. The composition of sugar chain, monosaccharide or mono