Protein bound carbohydrate

Mrochek, J. E., Dinsmore, S. R., Tormey, D. C., and Waalkes, T. P., Protein-bound carbohydrates in breast cancer, liquid-chromatographic analysis for mannose, galactose, fucose, and sialic acid in serum, Clin. Chem., 22, 1516, 1976. 

Harvey D.J. (2001), Identification of protein-bound carbohydrates by mass spectrometry, Proteomics 1, 311-328. 

Glycoproteins play an important role in, for example, immunology and the elucidation of the functions of the carbohydrate residues are therefore the focus of great current efforts. The protein-bound carbohydrates perform an array of functions ranging from protection against proteolysis to the complex interplay with receptors and the discrimination of these functions in simple model systems can perhaps aid in a more detailed understanding of protein-carbohydrate interactions. 

THE LIPID PATHWAY OF PROTEIN GLYCOSYLATION AND ITS INHIBITORS THE BIOLOGICAL SIGNIFICANCE OF PROTEIN-BOUND CARBOHYDRATES... 

An article by Li and Li (Tnlane University, LA) on the biosynthesis and catabolism of glycosphingolipids serves to extend that by Kiss (Vol. 24), which dealt mainly with the chemistry of these compounds. Schwarz and Datema (Giessen) provide a detailed account of the lipid pathway of protein glyeosylation and of its inhibitors, and then discuss the biological significance of protein-bound carbohydrates, thereby... 

G5. Goa, J., On protein-bound carbohydrates in human serum. Scand. J. Clin. Lab. Invest. 7, Suppl. 22 (1955). 

K14. Koiw, E., and Gronwall, A., Staining of protein-bound carbohydrates after electrophoresis of serum on filter paper. Scand. J. Clin, iz Lab. Invest. 2, 244... 

Jimenez-Barbero J, Asensio JL, Canada FJ, Poveda A. Free and protein-bound carbohydrate structures. Curr Opin Struct Biol 1999 Oct 9(5) 549-555. 

There is a temporary rise in mucoprotein and in protein-bound carbohydrate and hexosamine (B8a, B13, N4, P5). The response is greatly reduced if the liver is first poisoned (R8, WlOa). They rise in a great many infiammatory conditions (02). 

Schwarz RT, Datema R. The lipid pathway of protein glycosylation and its inhibitors the biological significance of protein-bound carbohydrates. Adv Carbohydr Chem Biochem 1982 40 287-379. 

H5 ercellular glomeruli and congestion of ihe convoluted tubules were observed in the kidneys of rats treated by gavage with tetrachloroethylene (3,000 mg/kg/day) in sesame oil for 42 days (Ebrahim et al. 1995). Significant increases in the levels of protein and protein-bound carbohydrates in the kidneys were also observed. No other doses of tetrachloroethylene were used in this study. Increased kidney/body weight ratios were observed in male rats treated with tetrachloroethylene in the drinking water at 400 mg/kg/day for 90 days (Hayes et al. 1986). No effects on the kidneys were observed at a dose of 14 mg/kg/day. 

Combined oral treatment of rats with tetrachloroethylene (3,000 mg/kg/day) and vitamin E (400 mg/kg/day) prevented the centrilobular necrosis in the liver and hypercellular glomeruli and congestion of convoluted tubules of the kidneys that was observed when rats were treated with tetrachloroethylene alone (Ebrahim et al. 1995). Vitamin E also prevented the tetrachloroethylene-induced increase in protein and protein-bound carbohydrates observed in the liver and kidneys of rats treated only with tetrachloroethylene. This study suggests that free radical metabolites may play a role in the liver and kidney toxicity observed in rats treated with tetrachloroethylene. 

In recent years numerous glycoproteins have been isolated and characterized, but the roles for the protein-bound carbohydrates have only just begun to be unravelled (1). It is now well established that glycosylation affects both the physiochemical properties and the biological functions of a glycoprotein. For instance, glycosylation has been found to influence uptake, distribution. 

Procedures have been described for the assay of protein-bound carbohydrate in sera and urine from normal children and from patients with sialuria. It was concluded that sialuria is not associated with an anomalous metabolism of glycoproteins, but with an anomalous biosynthesis of sialic acid. 

Eylar (1965) proposed that the function of protein-bound carbohydrate was as a signal for secretion of a particular protein species. This suggestion was based on the observation that most extracellular proteins contained carbohydrate, while intracellular proteins did not. The addition of carbohydrate would either be a signal or would be an intrinsic part of the secretion mechanism. This theory has been updated by Winterbum and Phelps (1972). The major problem with this proposal is that many proteins that are secreted do not contain carbohydrate (e.g., albumin). Also, many intracellular proteins do contain carbohydrate. Nevertheless, this proposal, in one form or another, is still the basis for current hypotheses on the role of bound carbohydrates. Schachter and Roden (1973) have modified this theory and suggest that the addition of carbohydrate is a signal for movement of molecules across membranes (internal as well as external). Those molecules which lack carbohydrate, but nevertheless have participated in such a mechanism, would have had it removed after the membrane transport step had occurred. 

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