Transferrin carbohydrate

Transferrins Carbohydrate Number of Types and number of glycan Fucosylation Bisecting GalNAc Figure... 

Alcohol consumption is very difficult to assess. There is widespread belief that individuals underreport their intake and there are no reliable laboratory tests available for definitive diagnosis of alcohol abuse. A combination of abnormalities in the plasma activity of gamma-glutamyl transferase (GGT or yGT), AST and reduction in erythrocyte mean cell volume (MCV) maybe useful and all are routine lab. tests. A potential marker of interest is carbohydrate-deficient transferrin (CDT) which is an abnormal isoform of serum transferrin arising due to defects in the attachment of carbohydrate chains to the protein core. Unfortunately, CDT is a somewhat specialized test, not performed by most laboratories. Other markers which have attracted some research interest are ethyl sulphate and ethyl glucuronide. Excretion in the urine of these metabolites occurs for up to 50 hours after binge drinking so they offer a useful index of recent heavy alcohol intake. 

Bacterial hosts are inappropriate choices for expression of proteins such as the blue copper proteins stellacyanin, laccase, and ceruloplasmin which are extensively glycosylated. In these cases, it may be necessary to employ tissue cultures of appropriate origin to obtain the native protein. In this regard, the amino-terminal half of human serum transferrin, which lacks carbohydrate, has been expressed in high yield in baby hamster kidney cells by Funk et al. [13], while the glycosylated carboxyl-terminus has proved to be more problematic [103]. 

Iron(III)-pyrophosphate looks promising as an alternative to iron(III)-carbohydrate preparations for parenteral administration for treatment of anemia.Kinetics of removal of iron from transferrin (tf) by pyrophosphate (pp) were found to be biphasic under certain conditions, with the rapid first phase attributed to the formation of a pp—Fe—tf—CO intermediate.A later study of the kinetics of removal of iron from transferrin employed pyrophosphate and tripodal phosphonates such as nitrilotris(methylenephosphonic acid), N(CH2P03H2)3. For the tripodal ligands there are parallel first-order and saturation pathways, with the latter dominant (contrast the exclusively first-order reaction of ferritin with nitrilotriacetate) for pyrophosphate the paths are roughly equal in importance. The saturation kinetics suggest that tfiFe-phosphonate intermediates play an important role in the kinetics. 

Final stage in the synthesis of a neura-minidate-containing carbohydrate unit of a glycoprotein (human transferrin). This terminal glycosylation takes place in the Golgi apparatus. 

Secretion of nonglycosylated macromolecules in the presence of tunicamycin has also been investigated in a number of other cells. Rat-liver cell-secretion ol albumin (a carbohydrate-free protein), transferrin, and a-acid glycoprotein was not inhibited, and, in chick-liver cells, only a decrease by 10-25% in the secretion of transferrin and the apoprotein B chain of very-low-density lipoprotein was noted.463,464 The secretion of ovalbumin (a glycoprotein) from hen oviduct was not blocked by tunicamycin.465... 

Iourin O, Mattu TS, Mian N, Keir G, Winchester B, Dwek RA, Rudd PM (1996) The identification of abnormal glycoforms of serum transferrin in carbohydrate deficient glycoprotein syndrome type I by capillary zone electrophoresis. Glycoconj J 13 1031-1042... 

Antibodies Carbohydrates Galactose Mannose Fucose Xylosyl Folic acid Transferrin... 

The transferrins contain varying amounts of carbohydrates (Table 7) and can be classified as glycoproteins. Williams (136) stated that ovotrans-ferrin and chicken serum transferrin differed only in carbohydrate contents. The ovotransferrin contains no sialic acid (44, 136). Serum transferrin, on the other hand, contains sialic acid. Williams (136), from the results of treating the serum transferrin with the enzyme neuraminidase, suggested that differences in the electrophoretic mobilities and isoelectric points of the multimolecular forms of serum transferrins may be due to differences in their contents of sialic acid. 

As compared to the information on the carbohydrate contents of human serum transferrin, much less information is available on lacto-transferrin. In general, however, the available values for lactotransferrin are more similar to those for serum transferrin than to those for ovotrans-ferrin. 

In general, the transferrins are all very similar with molecular weights reported in the range from approximately 70,000 to 90,000 g., and with nearly identical, if not identical, metal binding sites. In addition to variations in contents of amino acids, which normally occur in homologous proteins from different organs or species, the transferrins also vary in the amounts of carbohydrates and, of particular current interest, in the amounts of sialic acid. 

The relationships among the transferrins in the different fluids from the same individual are of obvious interest. Unfortunately, only limited data are available on this subject. A close immunological relationship of chicken serum transferrin and chicken ovotransferrin has been reported many times (20, 65, 79, 92, 136). Williams (136) in a detailed study by immunological methods, peptide mapping, and amino acid analyses reported that chicken serum transferrin and chicken ovotransferrin differ only in their carbohydrate prosthetic groups. 

Jamieson, G. A. Studies on glycoprotein II Isolation of the carbohydrate chains of human transferrin. J. Biol. Chem. 240, 2914 (1965). 

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