Isoelectric serum transferrin

Kilar, E and Hjerten,S., Fast and high resolution analysis of human serum transferrin by high performance isoelectric focusing in capillaries, Electrophoresis, 10, 23, 1989. 

Fig. 4.5.2 Actual strategies for CDG diagnosis. Initial investigations on CDG patients are routinely carried out by isoelectric focusing (IEF) of serum transferrin. With a CDG type I pattern, subsequent analysis should imply determination of phosphomannomutase (PMM) and phos-phomannose isomerase (PMI) activities. Further studies, like analysis of the lipid-linked- and protein-bound-oligosaccharides, determination of enzyme or sugar transporter activities and molecular biology studies often have to be performed in more specialised laboratories. HPLC High-performance liquid chromatography, TLC thin-layer chromatography...

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. 

Unlike Tf derived from serum, Tf from bloodstains present a secondary band for each allelic product. Transferrin has two iron binding sites and the monoferric form of Tf is the most stable. It appears that in bloodstains either binding site is available for iron. Depending upon the site occupied by iron the monoferric forms will have slightly different isoelectric points, and both monoferric forms will exist within a bloodstain. Thus, the monoferric form of Tf will produce two protein bands for each allelic product observed after ULPAGIF. This hypothesis is supported by the fact that these secondary bands do... 

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