"Vesel\u00E1, Kate\u0159ina" . "0141-8955" . "Wevers, Ron A" . . "Hans\u00EDkov\u00E1, Hana" . "Congenital Disorders of Glycosylation (CDG) form a group of metabolic disorders caused by deficient glycosylation of proteins and/or lipids. Isoelectric focusing (IEF) of serum transferrin is the most common screening method to detect abnormalities of protein N-glycosylation. On basis of the isofocusing profile, patients can be grouped in CDG type I or CDG type II. Secondary causes, such as the presence of a transferrin protein polymorphism can complicate interpretation and must be excluded before time-consuming diagnostics is initiated. Several protein variants of transferrin are known that result in a shift in pI and thereby result in double bands in IEF. Incubation of the plasma sample with neuraminidase can indicate the presence of a protein polymorphism by showing double bands at the position of asialotransferrin. Here, we present two cases with a novel protein polymorphism, resulting in a single transferrin isoform after neuraminidase digestion. Mass spectrometric analysis of immunopurified transferrin showed the presence of a non-glycosylated peptide, corresponding to the N-glycan consensus sequence of glycopeptide 2 in case 1 with the heterozygous p.Asn630Thr mutation and of glycopeptide 1 in case 2 with a heterozygous p.Asn432His mutation. Our results show the importance of mass spectrometry in the diagnostic track of CDG type I patients." . "Transferrin mutations at the glycosylation site complicate diagnosis of congenital disorders of glycosylation type I"@en . "235782" . . "13"^^ . "Van den Heuvel, LPWJ" . "Zeman, Ji\u0159\u00ED" . "34" . . "[D802B8D5B27D]" . . . . . "Transferrin mutations at the glycosylation site complicate diagnosis of congenital disorders of glycosylation type I"@en . "Transferrin mutations at the glycosylation site complicate diagnosis of congenital disorders of glycosylation type I" . . "Morava, Eva" . . "Ondru\u0161kov\u00E1, Nina" . . . . "000292829800008" . "Transferrin mutations at the glycosylation site complicate diagnosis of congenital disorders of glycosylation type I" . . "RIV/00064165:_____/11:10071!RIV12-MZ0-00064165" . . "4" . . . . "Guillard, Mailys" . "Wada, Yoshinao" . "http://dx.doi.org/10.1007/s10545-011-9311-y" . . . . . "6"^^ . "Janssen, Alice" . "Journal of Inherited Metabolic Disease" . "Lefeber, Dirk J" . . "RIV/00064165:_____/11:10071" . "I, Z(MSM0021620806)" . . "NL - Nizozemsko" . ": CHROMATOGRAPHY-MASS-SPECTROMETRY; DEFICIENT GLYCOPROTEIN SYNDROME; LIQUID-CHROMATOGRAPHY; VARIANTS; PROTEINS; CDG"@en . "Kadoya, Machiko" . "Yuasa, Isao" . "Congenital Disorders of Glycosylation (CDG) form a group of metabolic disorders caused by deficient glycosylation of proteins and/or lipids. Isoelectric focusing (IEF) of serum transferrin is the most common screening method to detect abnormalities of protein N-glycosylation. On basis of the isofocusing profile, patients can be grouped in CDG type I or CDG type II. Secondary causes, such as the presence of a transferrin protein polymorphism can complicate interpretation and must be excluded before time-consuming diagnostics is initiated. Several protein variants of transferrin are known that result in a shift in pI and thereby result in double bands in IEF. Incubation of the plasma sample with neuraminidase can indicate the presence of a protein polymorphism by showing double bands at the position of asialotransferrin. Here, we present two cases with a novel protein polymorphism, resulting in a single transferrin isoform after neuraminidase digestion. Mass spectrometric analysis of immunopurified transferrin showed the presence of a non-glycosylated peptide, corresponding to the N-glycan consensus sequence of glycopeptide 2 in case 1 with the heterozygous p.Asn630Thr mutation and of glycopeptide 1 in case 2 with a heterozygous p.Asn432His mutation. Our results show the importance of mass spectrometry in the diagnostic track of CDG type I patients."@en . "4"^^ .