Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: EC:2.7.7.48 (transcriptase)
 9,479 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The murine transformed cell line YC-8 and beta-adrenergic receptor agonist (isoproternol) treated rat and mouse parotid gland acinar cells ectopically express cell surface beta 1-4 galactosyltransferase during active proliferation. This activity is dependent upon the expression of the GTA-kinase (p58) in these cells. Using total RNA, cDNA clones for the protein coding region of the kinase were isolated by reverse transcriptase-PCR cloning. DNA sequence analysis failed to show sequence differences with the normal homolog from mouse cells although Southern blot analysis of YC-8, and a second cell line KI81, indicated changes in the restriction enzyme digestion profile relative to murine cell lines which do not express cell surface galactosyltransferase. The rat cDNA clone from isoproterenol-treated salivary glands showed a high degree of protein and nucleic acid sequence homology to the GTA-kinase from both murine and human sources. Northern blot analysis of YC-8 and a control cell line LSTRA revealed the synthesis of a major 3.0 kb mRNA from both cell lines plus the unique expression of a 4.5 kb mRNA in the YC-8 cells. Reverse transcriptase-PCR of LSTRA and YC-8 confirmed the increased steady state levels of the GTA-kinase mRNA in YC-8. In the mouse, induction of cell proliferation by isoproterenol resulted in a 50-fold increase in steady state mRNA levels for the kinase over the low level of expression in quiescent cells. Expression of the rat 3' untranslated region in rat parotid cells in vitro led to an increased rate of DNA synthesis, cell number an ectopic expression of cell surface galactosyltransferase in the sense orientation. Antisense expression or vector alone did not alter growth characteristics of acinar cells. A polyclonal antibody monospecific to a murine amino terminal peptide sequence revealed a uniform distribution of GTA-kinase over the cytoplasm of acinar and duct cells of control mouse parotid glands. However, upon growth stimulation, kinase was detected primarily in a perinuclear and nuclear immunostaining pattern. Western blot analysis confirmed a translocation from a cytoplasmic localization in both LSTRA and quiescent salivary cells to a membrane-associated localization in YC-8 and proliferating salivary cells.
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PMID:Characterization of the synthesis and expression of the GTA-kinase from transformed and normal rodent cells. 804 64

We studied the beta-1,3-galactosyltransferase (GalT) and alpha-1,2-fucosyltansferase (FT) involved in the biosynthesis of type-1-chain carbohydrate antigens in human colon adenocarcinoma cell lines. We detected a GalT activity able to use GlcNAc as acceptor and found that lacto-N-biose I (Galbeta1-3GlcNAc) is the only reaction product. Such beta1,3GalT is kinetically similar to a pig trachea enzyme involved in mucin synthesis. The specific activity is high in cells that react strongly with anti-Lewis a and anti-Lewis b antibodies, and undetectable in a cell line that lacks antibody reaction. Reverse-transcriptase-mediated PCR analysis followed by DNA sequencing indicated that secretor-type alpha1,2FT is expressed in the cells, while the H type alpha1,2FT is not. The apparent Km values for donor and acceptor substrates determined for alpha1,2FT are similar to those of secretor-type alpha1,2FT and the specific activity measured correlates with Lewis b antigen expression on the cell surface. Moreover, some of the cell lines express Lewis y and H type 2 antigens, indicating that secretor type alpha1,2FT is responsible for their synthesis. Results suggest that biosynthesis of type-1-chain tumor-associated antigens in human colon carcinoma cells is operated by secretor-type alpha1,2FT, as reported in normal mucosa, and that beta1,3GalT activity may play a relevant role in its control.
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PMID:Beta-1,3-galactosyltransferase and alpha-1,2-fucosyltransferase involved in the biosynthesis of type-1-chain carbohydrate antigens in human colon adenocarcinoma cell lines. 976 Jan 91

The large array of different glycolipids described in mammalian tissues is a reflection, in part, of diverse glycosyltransferase expression. Herein, we describe the cloning of a UDP-galactose: beta-d-galactosyl-1,4-glucosylceramide alpha-1, 3-galactosyltransferase (iGb(3) synthase) from a rat placental cDNA expression library. iGb(3) synthase acts on lactosylceramide, LacCer (Galbeta1,4Glcbeta1Cer) to form iGb(3) (Galalpha1,3Galbeta1, 4Glcbeta1Cer) initiating the synthesis of the isoglobo-series of glycosphingolipids. The isolated cDNA encoded a predicted protein of 339 amino acids, which shows extensive homology (40-50% identity) to members of the ABO gene family that includes: murine alpha1, 3-galactosyltransferase, Forssman (Gb(5)) synthase, and the ABO glycosyltransferases. In contrast to the murine alpha1, 3-galactosyltransferase, iGb(3) synthase preferentially modifies glycolipids over glycoprotein substrates. Reverse transcriptase-polymerase chain reaction revealed a widespread tissue distribution of iGb(3) synthase RNA expression, with high levels observed in spleen, thymus, and skeletal muscle. As an indirect consequence of the expression cloning strategy used, we have been able to identify several potential glycolipid biosynthetic pathways where iGb(3) functions, including the globo- and isoglobo-series of glycolipids.
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PMID:Expression cloning of a new member of the ABO blood group glycosyltransferases, iGb3 synthase, that directs the synthesis of isoglobo-glycosphingolipids. 1085 27

Plant cell walls are composed of a large number of complex polysaccharides, which contain at least 13 different monosaccharides in a multitude of linkages. This structural complexity of cell wall components is paralleled by a large number of predicted glycosyltransferases in plant genomes, which can be grouped into several distinct families based on conserved sequence motifs (B. Henrissat, G.J. Davies [2000] Plant Physiol 124: 1515-1519). Despite the wealth of genomic information in Arabidopsis and several crop plants, the biochemical functions of these coding regions have only been established in a few cases. To lay the foundation for the genetic and biochemical characterization of putative glycosyltransferase genes, we conducted a phylogenetic and expression analysis on 10 predicted coding regions (AtGT11-20) that are closely related to the MUR3 xyloglucan galactosyltransferase of Arabidopsis. All of these proteins contain the conserved sequence motif pfam 03016 that is the hallmark of the beta-d-glucuronosyltransferase domain of exostosins, a class of animal enzymes involved in the biosynthesis of the extracellular polysaccharide heparan sulfate. Reverse transcriptase-polymerase chain reaction and promoter:beta-glucuronidase studies indicate that all AtGT genes are transcribed. Although six of the 10 AtGT genes were expressed in all major plant organs, the remaining four genes showed more restricted expression patterns that were either confined to specific organs or to highly specialized cell types such as hydathodes or pollen grains. T-DNA insertion mutants in AtGT13 and AtGT18 displayed reductions in the Gal content of total cell wall material, suggesting that the disrupted genes encode galactosyltransferases in plant cell wall synthesis.
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PMID:Molecular analysis of 10 coding regions from Arabidopsis that are homologous to the MUR3 xyloglucan galactosyltransferase. 1502 Jul 58