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)

We report our discovery that many glycoproteins synthesized by Chinese hamster ovary (CHO) cells contain fucose in O-glycosidic linkage to polypeptide. To enrich for the possible presence of O-linked fucose, we studied the lectin-resistant mutant of CHO cells known as Lec1. Lec1 cells lack N-acetylglucosaminyltransferase I and are therefore unable to synthesize complex-type N-linked oligosaccharides. Lec1 cells were metabolically radiolabelled with [6-3H]fucose and total glycoproteins were isolated. Glycopeptides were prepared by proteolysis and fractionated by chromatography on a column of concanavalin A (Con A)-Sepharose. The sets of fractionated glycopeptides were treated with mild base/borohydride to effect the beta-elimination reaction and release potential O-linked fucosyl residues. The beta-elimination produced [3H]fucitol quantitatively from [3H]fucose-labelled glycopeptides not bound by Con A-Sepharose, whereas none was generated by treatment of glycopeptides bound by the lectin. The total [3H]fucose-labelled glycoproteins from Lec1 cells were separated by SDS-PAGE and detected by fluorography. Treatment of selected bands of detectable glycoproteins with mild base/borohydride quantitatively generated [3H]fucitol. Pretreatment of the glycoproteins with N-glycanase prior to the SDS-PAGE method of analysis caused an enrichment in the percentage of radioactivity recovered as [3H]fucitol. Trypsin treatment of [3H]fucose-labelled intact CHO cells released glycopeptides that contained O-linked fucose, indicating that it is present in surface glycoproteins. These findings demonstrate that many glycoproteins from CHO cells contain O-linked fucosyl residues and raise new questions about its biosynthesis and possible function.
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PMID:O-linked fucose in glycoproteins from Chinese hamster ovary cells. 813 Mar 91

D-Glucose entry into erythrocytes from adult dolphins (Tursiops truncatus) was rapid, showed saturation at high substrate concentrations, and demonstrated a marked stimulation by intracellular D-glucose. Kinetic parameters were estimated from the concentration dependence of initial rates of tracer entry at 6 degrees C: for zero-trans entry, Michaelis constant (K(m)) was 0.78 +/- 0.10 mM and maximal velocity (Vmax) was 300 +/- 9 mumol.l cell water-1.min-1; for equilibrium exchange entry, K(m) was 17.5 +/- 0.6 mM and Vmax was 8,675 +/- 96 mumol.l cell water-1.min-1. Glucose entry was inhibited by cytochalasin B, and mass law analysis of reversible, D-glucose-displaceable, cytochalasin B binding gave values of 0.37 +/- 0.03 nmol/mg membrane protein for maximal binding and 0.48 +/- 0.10 microM for the dissociation constant. Dolphin glucose transporter polypeptides were identified on sodium-dodecyl sulfate-polyacrylamide gel electrophoresis immunoblots [using antibodies that recognized human glucose transporter isoform (GLUT-1)] as two molecular species, apparent relative molecular weights of 53,000 and 47,000. Identity of these polypeptides was confirmed by D-glucose-sensitive photolabeling of membranes with [3H]cytochalasin B. Digestion of both dolphin and human red blood cell membranes with glycopeptidase F led to the generation of a sharp band of relative molecular weight 46,000 derived from GLUT-1. Trypsin treatment of human and dolphin erythrocyte membranes generated fragmentation patterns consistent with similar polypeptide structures for GLUT-1 in human and dolphin red blood cells.
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PMID:GLUT-1 mediation of rapid glucose transport in dolphin (Tursiops truncatus) red blood cells. 945 6

Autoantibodies to a 64-kD protein and a 40-kD tryptic fragment from pancreatic islets have been detected at high frequency in the sera of patients with insulin-dependent diabetes mellitus (IDDM). IA-2, a newly isolated transmembrane protein tyrosine phosphatase, is a major islet cell autoantigen in IDDM and the precursor of a 40-kD tryptic fragment. To express large quantities of recombinant IA-2 protein and analyse post-translational modifications we expressed full-length human IA-2 in baculovirus-infected Sf-9 cells. IA-2 expression was analysed by Western blot and by immunoprecipitation of 35S-methionine-radiolabelled proteins with rabbit antisera or IDDM sera. A 120-kD IA-2 protein was detected during the early, but not the late, phase of the infection. Pulse-chase experiments showed that the 120-kD protein was processed into fragments of 64 kD and smaller fragments of approximately 50 kD, 38 kD and 32 kD. The 64-kD fragment appeared as a doublet. Tunicamycin and PNGase F treatment down-shifted the 120-kD protein and the 64-kD doublet into lower molecular weight bands, suggesting that both were glycosylated. Trypsin treatment converted the 120-kD protein and the 64-kD doublet into a 40-kD fragment. Baculovirus-expressed IA-2 was as sensitive or slightly more sensitive than in vitro translated IA-2 in detecting autoantibodies to IA-2: 66% of sera from newly diagnosed IDDM patients reacted with baculovirus-expressed IA-2 compared with 59% of the same sera which reacted with in vitro translated IA-2. It is concluded that baculovirus-expressed IA-2 is a good source of autoantigen and that a number of lower molecular weight fragments with which IDDM autoantibodies react are derived from the 120-kD full-length IA-2 molecule.
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PMID:Expression, characterization, processing and immunogenicity of an insulin-dependent diabetes mellitus autoantigen, IA-2, in Sf-9 cells. 973 64

D-Glucose entry into erythrocytes from adult grey-headed flying fox fruit bats (Pteropus poliocephalus) was rapid and showed saturation at high substrate concentrations. Kinetic parameters were estimated from the concentration dependence of initial rates of zero-trans D-glucose entry at 5.5 degrees C as Michaelis constant (K(m)) 1. 64+/-0.56 mM, and maximal velocity (V(max)) 1162+/-152 micromol.l. cell water(-1).min(-1). D-Glucose entry was inhibited by cytochalasin B; mass law analysis of D-glucose-displaceable cytochalasin B binding gave values of K(d) 37.1+/-5.0 nM and B(max) 361.2+/-9.1 pmol/mg membrane protein. Entry of 2-deoxy-D-glucose, and 3-O-methyl-D-glucose, into P. poliocephalus red cells was rapid, entry of D-fructose was very slow. Glucose transporter polypeptides were identified on immunoblots as a band M(r) 47000-54000 and their identity confirmed by D-glucose-sensitive photolabeling of membranes with [3H]-cytochalasin B. Peptide-N-glycanase F digestion of both human and bat erythrocyte membranes generated GLUT-1-derived bands M(r) 37000. Trypsin digestion of human and fruit bat erythrocyte membranes generated fragmentation patterns consistent with similar GLUT-1 polypeptide structures in both species. Erythrocytes from adult Australian ghost bats (Macroderma gigas), a carnivorous microchiropteran bat, also expressed high levels of GLUT-1.
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PMID:Rapid GLUT-1 mediated glucose transport in erythrocytes from the grey-headed fruit bat (Pteropus poliocephalus). 1090 51