UNIPROT:Q07644 - FACTA Search

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Query: UNIPROT:Q07644 (polypeptide)
72,197 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Membrane preparations from pig gastric mucosa were shown to transfer [14C]GlcNAc from UDP-[14C]GlcNAc to blood group A-negative porcine submaxillary mucin previously subjected to mild acid hydrolysis to remove terminal sialyl and fucosyl residues. O-Glycosyl oligosaccharides were removed from enzyme product by alkaline borohydride treatment and, after purification, were subjected to high resolution proton nuclear magnetic resonance spectroscopy and methylation analysis. Two trisaccharide products were detected: [14C]GlcNAc beta 1-3Gal beta 1-3GalNAcOH and Gal beta 1-3[( 14C]GlcNAc beta 1-6)GalNAcOH. We have previously reported the in vitro synthesis of the latter compound, a branched trisaccharide, by UDP-GlcNAc:Gal beta 1-3GalNAc-R (GlcNAc to GalNAc) beta 6-N-acetylglucosaminyltransferase from canine submaxillary glands. However, this is the first report of the in vitro synthesis of the linear trisaccharide GlcNAc beta 1-3Gal beta 1-3GalNAc. Pig gastric mucosal beta 3-N-acetylglucosaminyltransferase catalyzed the formation of this trisaccharide by incorporation of GlcNAc into the terminal Gal of Gal beta 1-3GalNAc-alpha-R when R was a polypeptide from either mucin or antifreeze glycoprotein, but not when R was o-nitrophenyl. We have previously reported the in vitro synthesis by pig gastric mucosa of the tetrasaccharide GlcNAc beta 1-3Gal beta 1-3(GlcNAc beta 1-6)GalNAc-alpha-R when R was o-nitrophenyl or benzyl. We show in this report that pig gastric mucosa can synthesize this tetrasaccharide in vitro when R is a polypeptide from either porcine submaxillary mucin or antifreeze glycoprotein. Pig gastric mucosa therefore contains a beta 6-N-acetylglucosaminyltransferase capable of converting Gal beta 1-3GalNAc-alpha-R to Gal beta 1-3(GlcNAc beta 1-6)GalNAc-alpha-R and one or more beta 3-N-acetylglucosaminyltransferases which can add GlcNAc in beta 1-3 linkage to a terminal Gal residue to form either GlcNAc beta 1-3Gal beta 1-3GalNAc-alpha-R or GlcNAc beta 1-3Gal beta 1-3(GlcNAc beta 1-6)GalNAc-alpha-R where R is the polypeptide backbone of either mucin or antifreeze glycoprotein.
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PMID:Mucin synthesis. The action of pig gastric mucosal UDP-GlcNAc:Gal beta 1-3(R1)GalNAc-R2 (GlcNAc to Gal) beta 3-N-acetylglucosaminyltransferase on high molecular weight substrates. 624 Oct 35

Two size classes of O-glycosidically linked oligosaccharides were liberated from glycoprotein E1 of mouse hepatitis virus (MHV) A59 by reductive beta-elimination and separated by h.p.l.c. The structures of the reduced oligosaccharides were determined by successive exoglycosidase digestions and by methylation analyses involving combined capillary gas chromatography-mass spectrometry and mass fragmentography after chemical ionization with ammonia. Oligosaccharide A (Neu5Ac alpha 2----3 Gal beta 1----3 GalNAc) comprised 35% of the total carbohydrate side chains, while the remaining 65% of the oligosaccharides of E1 had the branched structure B: Neu5Ac alpha 2----3 Gal beta 1----3 (Neu5Ac alpha 2----6) GalNAc. Both oligosaccharides were linked to the E1 polypeptide via N-acetylgalactosamine, and 20% of the sialic acids present in E1 glycopeptides were found to consist of N-acetyl-9-mono-O-acetylneuraminic acid. The reported structures of the O-linked glycans are discussed in the context of the amino acid sequence of E1, which exhibits a cluster of four hydroxyamino acids (Ser-Ser-Thr-Thr) as potential O-glycosylation sites at the amino terminus. Oligosaccharides with identical structures and an identical O-glycosylated tetrapeptide sequence are present in the blood group M-active glycophorin A of the human erythrocyte membrane.
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PMID:The carbohydrates of mouse hepatitis virus (MHV) A59: structures of the O-glycosidically linked oligosaccharides of glycoprotein E1. 632 80

The Ca antigen, which can be detected in a wide range of malignant human tumours by means of the Cal antibody, is a glycoprotein of the mucin type. At least 95% of the carbohydrate is 0-glycosidically linked to the polypeptide which contains high proportions of glycine, serine and glutamic acid. The carbohydrate has a very simple structure: it is composed almost entirely of tetra- tri- and disaccharides having the general formula (NeuNac)n leads to [Gal leads to GalNac] alpha leads to, where n = 0, 1 or 2. In many malignant cell lines, the antigen is produced constitutively in vitro; but in one that has been examined, its synthesis can be induced by high concentrations of lactate. Evidence is presented for the view that a primary function of this glycoprotein is to shield the cells that produce it from hydrogen ion concentrations outside of the physiological range. The presence of the Ca antigen in malignant tumours may thus be a reflection of metabolic conditions that are known to be characteristics of such tumours.
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PMID:Structure and function of the Ca antigen. 634 73

Mucin glycoproteins were purified from extracts of swine trachea mucosa and Cowper's gland. The gelatinous extracts were solubilized by reduction and carboxymethylation and then purified by chromatography on Sepharose CL-6B and DEAE-Sepharose. The structure of some of the carbohydrate units in these glycoproteins were determined and compared. Alkaline borohydride treatment indicated that more than 85% of the carbohydrate chains in these glycoproteins were linked to serine or threonine residues in the polypeptide chain through O-glycosidic bonds with N-acetylgalactosamine. Reduced oligosaccharides released by treatment with alkaline borohydride were isolated by gel filtration on Bio-Gel P-6 and chromatography on DEAE-cellulose and paper. The structures of the oligosaccharides were established by methylation analysis, gas chromatography, and sequential hydrolysis with specific exoglycosidases. The major oligosaccharides in Cowper's gland mucin glycoproteins were sialylated short chains: NeuAc alpha 2,6GalNAcol and NeuAc alpha 2,3Gal beta 1,3(NeuAc alpha 2,6)GalNAcol. In marked contrast, branched chains containing a Gal beta 1,3(GlcNAc beta 1,6)GalNAc core unit were the major components of trachea mucin glycoprotein. Ten of these chains had the following structures: (Formula: see text).
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PMID:Purification and structures of oligosaccharide chains in swine trachea and Cowper's gland mucin glycoproteins. 643 40

The preceding paper (Williams, D., and Schachter, H. (1980) J. Biol. Chem. 255, 0000-0000) described a novel N-acetylglucosaminyltransferase in canine submaxillary gland microsomes which catalyzed the incorporation of GlcNAc into mucin acceptors. We show in the present report that the enzyme catalyzes th following reaction: UDP-GlcNAc + Gal beta 1-3GalNAc-X leads to Gal beta 1-3(GlcNAc beta 1-6) GalNAc-X + UDP, where X can be porcine submaxillary mucin polypeptide (Km = 5.2 mM), antifreeze glycoprotein polypeptide (Km = 23 mM), alpha-O-p-nitrophenyl (Km = 0.52 mM), beta-O-p-nitrophenyl (Km = 0.92 mM), alpha-O-o-nitrophenyl (Km = 0.86 mM), alpha-O-benzyl (Km = 0.77 mM), alpha-O-methyl (Km = 4.2 mM), or -H (Km = 1.2 mM). Ineffective acceptors (< 5% of the activity with Gal beta 1-3GalNAc-alpha-p-nitrophenyl) are asialo-ovine submaxillary mucin, asialo-alpha 1 acid glycoprotein, Gal beta 1-3GlcNAc-beta-p-nitrophenyl, Gal beta 1-3GlcNAc-alpha-methyl, Gal beta1-3GlcNAc, Gal beta 1-3-N-acetylgalactosaminitol, and D-fucose beta 1-3GalNAc-alpha-benzyl, indicating that both the Gal and GalNAc residues are essential for acceptor activity. The beta 1 leads to 6-linkage of GlcNAc to GalNAc in the acceptor Gal beta 1-3GalNAc-alpha-O-benzyl was established by methylation analysis and high resolution 1H nuclear magnetic resonance spectroscopy of a large scale preparation of product. Preliminary evidence has been obtained indicating that sialic acid linked alpha 2-6 to GalNAc or L-fucose linked alpha 1-2 to Gal inhibit the action of the beta 6-N-acetylglucosaminyltransferase on Gal beta 1-3GalNAc-porcine submaxillary mucin polypeptide.
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PMID:Mucin synthesis. II. Substrate specificity and product identification studies on canine submaxillary gland UDP-GlcNAc:Gal beta 1-3GalNAc(GlcNAc leads to GalNAc) beta 6-N-acetylglucosaminyltransferase. 644 8

Canine submaxillary gland microsomes have been shown to catalyze the following reaction: UDP-GlcNAc + Gal beta 1-3GalNAc-X leads to Gal beta 1-3(GlcNAc)GalNAc-X + UDP where X is porcine or ovine submaxillary mucin polypeptide or a low molecular weight substituent. This activity was shown by mixed substrate experiments to be different from two other previously described glycoprotein N-acetylglucosaminyltransferases acting on N-glycosyl oligosaccharides and is the first N-acetylglucosaminyltransferase shown to act on mucin substrates. The transferase-catalyzed reaction proceeds at 70 to 80% of the optimum rate in the absence of added divalent cation or in the presence of 10 mM EDTA. The enzyme appeared to be unstable at 37 degrees C, but the reaction rate remained constant for at least 2 h at 25 degrees C. The enzyme showed a pH optimum of 7.0 and was stimulated 4-fold by 0.125% Triton X-100. Methylation analysis of product formed either with mucin acceptor or Gal beta 1-3GalNAc-alpha-O-benzyl indicated GlcNAc transfer to either carbon 4 or carbon 6 of the GalNAc residue of the acceptors.
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PMID:Mucin synthesis. I. Detection in canine submaxillary glands of an N-acetylglucosaminyltransferase which acts on mucin substrates. 644 7

A variant of the MM glycoprotein (glycophorin A) was isolated from erythrocyte membranes of two individual donors, a mother (L.G.) and daughter (V.W.). This glycoprotein was found to be a carbohydrate variant in which, for both donors, certain O-glycosidically linked saccharides retained the core structure consisting of NeuAc(alpha 2,3)Gal(beta 1,3)GalNAc that is common to all O-linked saccharides of the MN glycoproteins, and, in addition, contained substituents, of varying chain lengths, on the primary carbinol of GalNAc. These saccharides were released from the polypeptide by beta-elimination in the presence of sodium borohydride, and aspects of their structure were investigated by glycosidase digestion and periodate oxidation. Thus, the smallest variant structure was deduced to be NeuAc(alpha 2,3)Gal(beta 1,3)[GlcNAc(beta 1,6)]H2GalNAc. The 6-O-linked GlcNAc appears to serve as the focus of further chain elongation reactions, involving alternate additions of Gal and GlcNAc residues and leading to the formation of several homologous structures. Two such structures, NeuAc(alpha 2,3)Gal(beta 1,3)[GlcNAc(beta 1,?) Gal(beta 1,3/4)GlcNAc(beta 1,6)]H2GalNAc and NeuAc(alpha 2,3) Gal(beta 1,3)[Gal(beta 1,3/4)GlcNAc(beta 1,6)]H2GalNAc were the predominant species present. A larger saccharide was also isolated and its partial sequence was determined to be Gal(beta 1,3/4)GlcNAc(beta 1,?)[Gal(beta 1,3/4)Glc-NAc(beta 1,?)] Gal(beta 1,3/4)GlcNAc(beta 1,6)[NeuAc(alpha 2,3)Gal-(beta 1,3)]H2GalNAc. Because the peptide portion of these glycoproteins contains two methionine residues, it was possible to isolate two CNBr glycopeptides from separate regions of the molecule, and to assess the distribution of these variant structures in the polypeptide. The saccharides were linked to about 2-3 Ser and/or Thr residues in the donor LG glycoprotein and one of the attachment sites was located within the CNBr glycooctapeptide representing the NH2 terminus. Considerable heterogeneity in saccharide structure was documented for this site, and it is likely that such heterogeneity occurs also at other sites. The variant saccharides bear structural similarities to the core region of O-linked saccharides of certain blood group-active mucins and ovarian cyst secretions, and to the outer sequences of N-linked carbohydrate units (I-, i-active) of the major glycoprotein of human erythrocytes, band 3. The structures of the variant saccharides suggest that they may be potential precursors of H blood group-active carbohydrates, present in varying degrees of maturity, and attached to an integral protein of erythrocytes.
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PMID:A carbohydrate structural variant of MM glycoprotein (glycophorin A). 661 26

Human chorionic gonadotropin (hCG) highly purified from urine of the patient with choriocarcinoma contains four asparagine-linked sugar chains in one molecule. The sugar chains were quantitatively liberated as radioactive oligosaccharides from polypeptide portion by hydrazinolysis followed by N-acetylation and NaB3H4 reduction. The structures of these sugar chains were determined by the combination of sequential glycosidase digestion, periodate oxidation, and methylation analysis. As compared with the sugar chains of normal urinary and placental hCG reported previously, they include several prominent structural differences. More than 97% of the sugar chains of choriocarcinoma hCG was free from sialic acid, while the sugar chains of normal hCG were mostly sialylated. Choriocarcinoma hCG contains unusual biantennary complex-type sugar chains in addition to regular tri-, bi-, and monoantennary sugar chains. These sugar chains have two outer chains linked at the C-2 and C-4 positions of the same alpha-mannosyl residue of the trimannosyl core. Since normal hCG does not contain any triantennary sugar chains, occurrence of Gal beta 1 leads to 4GlcNAc beta 1 leads to 4Man alpha 1 leads to group is another characteristic feature of the sugar chains of choriocarcinoma hCG. The evidence that the monoantennary sugar chain of Man alpha 1 leads to 6(Gal beta 1 leads to 4GlcNAc beta 1 leads to 2Man alpha 1 leads to 3)Man beta 1 leads to 4GlcNAc beta 1 leads to 4(Fuc alpha 1 leads to 6)GlcNAc leads to Asn is not found in normal hCG and the sum total of fucosylated sugar chains is 50%, which is twice as much as normal hCG, indicated that fucosylation is also modified in choriocarcinoma tissue.
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PMID:Structures of the asparagine-linked sugar chains of human chorionic gonadotropin produced in choriocarcinoma. Appearance of triantennary sugar chains and unique biantennary sugar chains. 664 71

The carbohydrate structure and complete amino acid sequence of a human lambda-type immunoglobulin light chain, protein Sm lambda has been determined. The protein was isolated from the urine of a patient with a plasma cell dyscrasia resembling gamma-heavy-chain disease. 13 tryptic peptides covering the entire polypeptide chain of 135 residues were isolated from the aminoethylated protein, and 15 chymotryptic peptides, accounting for 131 residues, were recovered from the carboxymethylated protein. The sequence of 18 of these peptides was partially or completely determined by the Edman-dansyl technique or C-terminal analysis, permitting the establishment of the complete primary structure of the polypeptide chain. The sequences established that this light chain possessed an intramolecular deletion of 81 amino acid residues. The N-terminal 30 residues showed considerable homology with other lambda chains of subgroup II. The defect began at position 31, in the first hypervariable region, and encompassed the remainder of the variable region through position 109. The constant region was fully intact and normal synthesis recommenced with a glutaminyl residue at position 110, the first residue of the constant region. This light chain contained carbohydrate in the hypervariable region just preceding the deletion. The precise number and locations of the oligosaccharide chains were established by amino acid sequence analysis of glycopeptides isolated from proteolytic hydrolysates by chromatography on Bio-Gel P-6 columns. These studies showed that protein Sm lambda contains one N-glycosidically-linked chain attached to asparagine-25 and one O-glycosidically-linked oligosaccharide chain attached to serine-21. The structures of the oligosaccharide chains were determined by methylation analysis, gas chromatography and hydrolysis with specific glycosidases. The structure of the N-glycosidically-linked chain was NeuAc(alpha 2 leads to 6)Gal(beta 1 leads to 4)GlcNAc(beta 1 leads to 2)Man(alpha 1 leads to 6)[NeuAc(alpha 2 leads to 6)Gal(beta 1 leads to 4)GlcNAc(beta 1 leads to 2)Man(alpha 1 leads to 3)]Man(beta 1 leads to 4)GlcNAc(beta 1 leads to 4)[Fuc alpha 1 leads to 6]GlcNAc leads to Asn. The second O-glycosidically-linked chain was a disialylated tetrasaccharide with the structure, Neu(alpha 2 leads to 3)Gal(beta 1 leads to 3)[NeuAc(alpha 2 leads to 6)GalNAc leads to Ser. This mucin-type disialylated tetrasaccharide in close proximity to N-asparagine-linked chains has not been previously observed in the oligosaccharide chains of immunoglobulins.
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PMID:Localization of the carbohydrate units in a human immunoglobulin light chain, protein Sm lambda. 678 88

An in vitro method for culturing Limax maximus albumen glands is described in which the biosynthetic activity of the slug albumen gland was monitored by measuring the incorporation of [14C]glucose into galactogen. Homogenates of the central nervous system were shown to cause a 3.5- to 12-fold increase in galactogen synthesis in albumen gland explants as compared to controls. The major sources of the galactogen-synthesis stimulating factor (Gal-SF) were found to be the cerebral ganglia and their surrounding connective tissue. Gal-SF was demonstrated to be peptidase sensitive and heat labile suggesting that it is probably a polypeptide. Autoradiographs of semithin araldite sections supported the incorporation data: in albumen gland explants cultured with cerebral ganglion homogenate considerably more label was found over secretory granules than in control-cultured explants. The possible cellular source of Gal-SF is discussed in relation to its possible origin in other investigated pulmonates.
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PMID:Endocrine control of galactogen synthesis in the albumen gland of the slug, Limax maximus. 684 May 25

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