Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:3.5.1.52 (PNGase F)
1,527 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Recently the genomic sequences of three multicellular eukaryotes, Caenorhabditis elegans, Drosophila melanogaster and Arabidopsis thaliana, have been elucidated. A number of cDNAs encoding glycosyltransferases demonstrated to have a role in N-linked glycosylation have already been cloned from these organisms, e.g., GlcNAc transferases and alpha 1,3-fucosyltransferases. However, many more homologues of glycosyltransferases and other glycan modifying enzymes have been predicted by analysis of the genome sequences, but the predictions of full length open reading frames appear to be particularly poor in Caenorhabditis. The use of these organisms as models in glycobiology may be hampered since they all have N-linked glycosylation repertoires unlike those of mammals. Arabidopsis and Drosophila have glycosylation similar to that of other plants or insects, while our new data from MALDI-TOF analysis of PNGase A-released neutral N-glycans of Caenorhabditis indicate that there exists a range of pauci- and oligomannosidic structures, with up to four fucose residues and up to two O-methyl groups. With all these three 'genetic model organisms', however, much more work is required for a full understanding of their glycobiology.
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PMID:Genetic model organisms in the study of N-glycans. 1153 Feb 1

The state of protein glycosylation in terms of occupation of potential N-linked glycosylation sites (macroheterogeneity) and type of glycosylation at that site (microheterogeneity) is important when investigating the consequences of aberrant glycosylation in the pathophysiology of disease. Protocols have been developed to permit characterisation of the site-specific glycosylation of individual isoforms of glycoproteins after separation by two-dimensional polyacrylamide gel electrophoresis (2D-PAGE) and analysis of the peptide mixture by peptide mass fingerprinting using matrix-assisted laser desorption/ionisation-time of flight mass spectrometry (MALDI-TOF). High resolution of the individual isoforms of alpha 1-antitrypsin was achieved by using narrow range (4.5-5.5) p/strips. The individual isoforms were then subjected to sequential digestion with a recombinant N-glycanase followed by a protease. Using this strategy it was possible not only to increase the coverage of the amino acid sequence but also to monitor the occupancy of all three putative N-linked glycosylation sites. Glycans were enzymatically released from alpha 1-antitrypsin which had been separated in gels formed with a low percentage of bis-acrylamide cross-linker and analysed. Profiles of the N-linked glycans of the individual isoforms of alpha 1-antitrypsin were obtained by MALDI-TOF.
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PMID:Analysis by matrix assisted laser desorption/ionisation-time of flight mass spectrometry of the post-translational modifications of alpha 1-antitrypsin isoforms separated by two-dimensional polyacrylamide gel electrophoresis. 1167 85

Gp273, a glycoprotein of the egg extracellular coats of the mollusc bivalve Unio elongatulus, is the ligand molecule for sperm-egg interaction during fertilization. In this study we have analyzed the N-glycans from gp273. N-glycans were enzymatically released by PNGase F digestion and their structures were elucidated by normal phase HPLC profiling of the 2-aminobenzamide-labeled N-glycans, MALDI-TOF mass spectrometry and 1H NMR spectroscopy. The combined data revealed that the N-glycans of gp273 consist of Glc1Man9GlcNAc2 and Man9GlcNAc2. In Unio, the presence of noncomplex-type N-glycans parallels the inefficacy of these glycans in the ligand function. Their role in the protection of the polypeptide chain from proteolytic attack is suggested by the electrophoretic patterns obtained after enzymatic digestion of the native and the N-deglycosylated protein. These results are discussed in the light of the evolution of the recognition and adhesion properties of oligosaccharide chains in the fertilization process.
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PMID:Structural characterization of the N-glycans of gp273, the ligand for sperm-egg interaction in the mollusc bivalve Unio elongatulus. 1215 12

Mass spectrometric techniques combined with enzymatic digestions were applied to determine the glycosylation profiles of cellobiohydrolase (CBH II) and endoglucanases (EG I, II) purified from filamentous fungus Trichoderma reesei. Electrospray mass spectrometry (ESMS) analyses of the intact cellulases revealed the microheterogeneity in glycosylation where glycoforms were spaced by hexose units. These analyses indicated that glycosylation accounted for 12-24% of the molecular mass and that microheterogeneity in both N- and O-linked glycans was observed for each glycoprotein. The identification of N-linked attachment sites was carried out by MALDI-TOF and capillary liquid chromatography-ESMS analyses of tryptic digests from each purified cellulase component with and without PNGase F incubation. Potential tryptic glycopeptide candidates were first detected by stepped orifice-voltage scanning and the glycan structure and attachment site were confirmed by tandem mass spectrometry. For purified CBH II, 74% of glycans found on Asn310 were high mannose, predominantly Hex(7-9)GlcNAc(2), whereas the remaining amount was single GlcNAc; Asn289 had 18% single GlcNAc occupancy, and Asn14 remained unoccupied. EG I presented N-linked glycans at two out of the six potential sites. The Asn56 contained a single GlcNAc residue, and Asn182 showed primarily a high-mannose glycan Hex(8)GlcNAc(2) with only 8% being occupied with a single GlcNAc. Finally, EG II presented a single GlcNAc residue at Asn103. It is noteworthy that the presence of a single GlcNAc in all cellulase enzymes investigated and the variability in site occupancy suggest the secretion of an endogenous endo H enzyme in cultures of T. reesei.
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PMID:Identification of glycan structure and glycosylation sites in cellobiohydrolase II and endoglucanases I and II from Trichoderma reesei. 1249 6

Human C1 inhibitor (hC1INH) is a therapeutic N, O-glycoprotein with a growing number of clinical applications, but the current natural supplies are not likely to meet the clinical demands. Therefore, recombinant approaches are of interest, whereby specific attention has to be paid to the generated glycosylation patterns. Here, the N,O-glycoprotein was expressed in the mammary gland of transgenic rabbits and subjected to glycan analysis. After release of the N-glycans of recombinant-rabbit human C1 inhibitor (rhC1INH) by peptide-N4-(N-acetyl-beta-glucosaminyl)asparagine amidase F, the oligosaccharides were separated from the O-glycoprotein by centrifugal filtration, then fractionated by a combination of anion-exchange, normal-phase, and high-pH anion-exchange liquid chromatography. The O-glycans, released from the O-glycoprotein by alkaline borohydride treatment, were fractionated by anion-exchange high-performance liquid chromatography (HPLC). The structures of individual components were analysed by 500 MHz 1H NMR spectroscopy, in most cases combined with MALDI-TOF MS. In contrast to the structural data reported for native serum hC1INH, rhC1INH contained a broad array of different N-glycans, made up of oligomannose-, hybrid-, and complex-type structures. In the case of complex-type N-glycans (partially) (alpha2-6)-sialylated (N-acetylneuraminic acid only), mono- and diantennary chains were found; part of the diantennary structures were (alpha1-6)-core-fucosylated or (alpha1-3)-fucosylated in the lower or upper antenna (Lewis x). The manno-oligosaccharide pattern of part of the hybrid- and oligomannose-type structures indicates that besides the usual N-glycan processing route, also the alternative endo-mannosidase pathway is followed. The small core 1-type O-glycans showed the usual (alpha2-3)- and (alpha2-6)-sialylation pattern of O-glycoproteins of nonmucinous origin.
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PMID:N- and O-glycans of recombinant human C1 inhibitor expressed in the milk of transgenic rabbits. 1451 17

To identify factors required for the synthesis of complex glycans, we have isolated Chinese hamster ovary (CHO) cell mutants resistant to plant lectins. We previously identified Lec19 CHO cells as resistant to the Gal-binding lectins ricin, abrin, and modeccin and hypersensitive to the toxicity of other lectins that bind Gal, including L-PHA and E-PHA. Here we show that Lec19 cell extracts have a decreased ability to transfer Gal to simple sugar, oligosaccharide, and glycopeptide acceptors, particularly to biantennary, GlcNAc-terminated acceptors. Ricin(II)-agarose lectin affinity chromatography, oligomapping, and monosaccharide analyses provided evidence that Lec19 N-glycans have fewer Gal residues than CHO N-glycans. MALDI-TOF mass spectra of N-glycans released from Lec19 cell glycoproteins by peptide N-glycanase F revealed species with the predicted masses of neutral N-glycans with few Gal residues. Such truncated species are essentially absent from CHO cell glycoproteins. However, the complement of fully galactosylated or sialylated bi-, tri-, and tetra-antennary N-glycans was largely equivalent in Lec19 and CHO cells. In addition, the coding region sequences of the beta4GalT-1, -T-2, -T-3, -T-4, -T-5, and -T-6 genes were identical in CHO and Lec19 cells. However, Northern analyses revealed an approximately 2-4-fold reduction in the level of transcripts of all six beta4GalT genes in Lec19 cells. Since the recessive Lec19 phenotype is the result of a loss-of-function mutation, the combined data predict the existence of a trans-acting regulator of the steady-state level of transcripts that derive from these six mammalian beta4GalT genes.
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PMID:A mutation causing a reduced level of expression of six beta4-galactosyltransferase genes is the basis of the Lec19 CHO glycosylation mutant. 1456 96

Mass spectrometry has been shown in recent years to be a powerful tool to determine accurate molecular masses and sequences of peptides and proteins and post-translational modifications such as glycosylation, phosphorylation, and sulfation. For glycosylation, it has been increasingly recognized to be of pivotal importance to identify whether potential glycosylation sites are actually modified by glycans, because functions of proteins may be modulated or depend on the presence of glycans at specific sites. Several recent reports have established that mass spectrometric techniques such as matrix-assisted laser desorption/ionization or electrospray ionization mass spectrometry (MALDI-TOF or ESI-MS, respectively) with or without preceding HPLC and in combination with PNGase F treatment are suited to analyze whether consensus sequences for N-glycosylation are glycosylated or not. Here we report the mass spectrometric analysis of the six potential N-glycosylation sites of the neural cell adhesion molecule NCAM from adult mouse brain. Unmodified peptides and glycopeptides each carrying a single glycosylation site were generated from NCAM by AspN and trypsin treatment and submitted to reversed-phase HPLC with or without prior enzymatic release of N-glycans. The resulting peptides were analyzed by MALDI-TOF-MS. In addition, high-resolution Fourier transform-ion cyclotron resonance (MALDI-FTICR) mass spectrometry was performed after in-gel deglycosylation and subsequent trypsin digestion. By using these procedures all six consensus sequences were shown to be glycosylated; the observation of an unmodified peptide with the consensus sequence N-1 indicates only partial glycosylation at this site.
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PMID:Identification of N-glycosylation sites of the murine neural cell adhesion molecule NCAM by MALDI-TOF and MALDI-FTICR mass spectrometry. 1465 30

N-acetylglucosaminyltransferase V (GnT-V) catalyzes the addition of a beta1,6-linked GlcNAc to the alpha1,6 mannose of the trimannosyl core to form tri- and tetraantennary N-glycans and contains six putative N-linked sites. We used mass spectrometry techniques combined with exoglycosidase digestions of recombinant human GnT-V expressed in CHO cells, to identify its N-glycan structures and their sites of expression. Release of N-glycans by PNGase F treatment, followed by analysis of the permethylated glycans using MALDI-TOF MS, indicated a range of complex glycans from bi- to tetraantennary species. Mapping of the glycosylation sites was performed by enriching for trypsin-digested glycopeptides, followed by analysis of each fraction with Q-TOF MS. Predicted tryptic glycopeptides were identified by comparisons of theoretical masses of peptides with various glycan masses to the masses of the glycopeptides determined experimentally. Of the three putative glycosylation sites in the catalytic region, peptides containing sites Asn 334, 433, and 447 were identified as being N-glycosylated. Asn 334 is glycosylated with only a biantennary structure with one or two terminating sialic acids. Sites Asn 433 and 447 both contain structures that range from biantennary with two sialic acids to tetraantennary terminating with four sialic acids. The predominant glycan species found on both of these sites is a triantennary with three sialic acids. The appearance of only biantennary glycans at site Asn 433, coupled with the appearance of more highly branched structures at Asn 334 and 447, demonstrates that biantennary acceptors present at different sites on the same protein during biosynthesis can differ in their accessibility for branching by GnT-V.
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PMID:Analysis of the site-specific N-glycosylation of beta1,6 N-acetylglucosaminyltransferase V. 1508 11

Human serum acid alpha-1-glycoprotein (AGP, orosomucoid) content of healthy individuals and cancer patients was measured, isolated and purified using a protocol of fast and biocompatible sample preparation, ion exchange and dye-ligand affinity chromatographic methods. In comparison to the healthy individuals significantly higher serum AGP levels were found in a wide spectrum of cancer patients, indicating its diagnostic value in the malignant disease. Oligosaccharide content of AGP samples was separated following PNGase F enzyme digestion and analysed by RP-HPLC and MALDI-TOF mass spectrometry. RP-HPLC and MALDI-TOF mass spectrometric analysis of sugar constituents of AGP specimen originated from selected cancer patients with high serum AGP levels indicated the appearance of anomal distribution of bi-, tri- and tetra-antennary oligosaccharide structures compared to the healthy controls.
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PMID:Liquid chromatographic and mass spectrometric analysis of human serum acid alpha-1-glycoprotein. 1523 41

Glycosylated proteins on the cell surface have been shown to be essential for cell-cell interactions in development and differentiation. Our ultimate goal is to identify Asn-linked oligosaccharides that are directly involved in these critical in vivo functions. Because such oligosaccharides would be expected to reside on the integral plasma membrane proteins, and conventional two-dimensional gel techniques are ineffective at separating such proteins, we have developed a new approach to their identification on a proteomics scale from Caenorhabditis elegans. Membrane proteins are solubilized in guanidine-HCl, precipitated, and digested with trypsin. The glycopeptides are then separated by lectin chromatography. Next, glycopeptidase F digestion removes the oligosaccharides from the peptides and converts to Asp each Asn to which one was attached. The peptides are then analyzed by matrix-assisted laser desorption/ionization quadrupole time-of-flight (MALDI-Q-TOF) mass spectrometry. Thus, the membrane glycoproteins are identified through the sequence tags of these peptides and the conversion of at least one deduced Asn residue to Asp at the Asn-X-Ser/Thr consensus sequence. To validate the utility of this approach, we have identified 13 membrane-bound N-glycosylated proteins from the major peaks observed on MALDI-Q-TOF analysis of our total glycopeptide fraction.
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PMID:A method for proteomic identification of membrane-bound proteins containing Asn-linked oligosaccharides. 1530 63


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