Trisialo transferrin

Fig. 4.5.3 IEF patterns of serum transferrin. Sera from a control (lane 1), three CDG-I (CDG-Ia, CDG-Ic and CDG-Id lanes 2-4) and three CDG-II patients (CDG- , CDG-IId and CDG-IIx lanes 5-7) were analysed by IEF. In case of a control person, the main form of the protein carries four negatively charged sialic acid residues, even though small amounts of penta- and trisialo-transferrin are detectable. Additional disialo- and asialotransferrin forms indicate CDG-type I (left side). In some cases of CDG type II, additional trisialo- and monosialotransferrin forms may occur, which are due to the loss of either one or three sialic acid residues (right side). Isoforms of transferrin that are independent of a pathological phenotype and that cause double bands in IEF are visible in lanes 4 and 6. CDG-IIx indicates a transferrin pattern that is caused by a so far unknown molecular defect from the CDG-II type...

Fig. 4.5.4 Identification of mutations in the transferrin protein by neuraminidase treatment. Unusual patterns in the IEF of serum transferrin might lead to pitfalls in CDG diagnostics. These varying patterns are often due to mutations of charged amino acids in the protein backbone of the transferrin molecule, which might lead, for example, to an accumulation of trisialo transferrin bands (lane 3, indicated by a question mark). Further investigations are carried out by cleaving off charged sialic acid monosaccharide moieties from transferrin-linked oligosaccharides by neuraminidase treatment, followed by IEF and transferrin antibody staining. In the case of protein mutations, additional bands below (lane 4) or above (not shown) the desialylated transferrin form appear...

L. Dibbelt, Does trisialo-transferrin provide valuable information for the laboratory diagnosis of chronically increased alcohol consumption by determination of carbohydrate-deficient transferrin , Clin. Chem., 46, 1203-1205 (2000). 

In healthy individuals, tetrasialotransferrin normally accounts for about 75-80% of serum transferrin, whereas trisialo- and pentasialotransferrin make up < 5 and 10—15%, respectively, and disialotransfenin 0.5-2% (mean 1.16%). Patients who admitted drinking alcohol in the previous week (range 15-780 g day ) typically showed elevated values of disialotransferrin (mean 4.25%). Asialotransferrin, which is not detectable in serum from... 

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