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James W.m. Yung - One of the best experts on this subject based on the ideXlab platform.
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Studies on uridine diphosphate-galactose pyrophosphatase and uridine diphosphate-galactose: glycoprotein galactosyltransferase activities in microsomal membranes.
Archives of Biochemistry and Biophysics, 2004Co-Authors: Sailen Mookerjea, James W.m. YungAbstract:Abstract Rat liver microsomes showed very active uridine diphosphate-galactose pyrophosphatase activity leading to the hydrolysis of uridine diphosphate-galactose into galactose1-phosphate and finally into galactose. The activity was observed in presence of buffers with wide ranges of pH. Different concentrations of divalent cations, such as Mn 2+ , Mg 2+ , and Ca 2+ had no significant effect on the enzyme activity. A number of nucleotides and their derivatives inhibited the pyrophosphatase activity. Of these, different concentrations of uridine monophosphate, Cytidine 5′-phosphate and Cytidine 5′-diphosphate have slight or no effect; Cytidine 5′-triphosphate, adenosine 5′-triphosphate, guanosine 5′-triphosphate, Cytidine 5′-diphosphate-glucose and guanosine 5′-diphosphate-glucose showed strong inhibitory effect whereas Cytidine 5′-diphosphate-choline showed a moderate effect on the pyrophosphatase. All these nucleotides also showed variable stimulatory effects on uridine diphosphate-galactose:glycoprotein galactosyltransferase activity in the microsomes which could be partly related to their inhibitory effects on uridine diphosphate-galactose pyrophosphatase. Among them uridine monophosphate, Cytidine 5′-phosphate, and Cytidine 5′-diphosphate stimulated galactosyltransferase activity without showing appreciable inhibition of pyrophosphatase, Cytidine 5′-diphosphate-choline, although did not inhibit pyrophosphatase as effectively as Cytidine 5′-triphosphate, guanosine 5′-triphosphate, adenosine 5′-triphosphate, Cytidine 5′-diphosphate-glucose, and guanosine 5′-diphosphate-glucose but stimulated galactosyltransferase activity as well as those. The fact that Cytidine 5′-diphosphate-choline stimulated galactosyltransferase more effectively than Cytidine 5′-phosphate, Cytidine 5′-diphosphate, and Cytidine 5′-triphosphate suggested an additional role of the choline moiety in the system. It has been also shown that Cytidine 5′-diphosphate-choline can affect the saturation of galactosyltransferase enzyme at a much lower concentration of uridine diphosphate-galactose. Most of the pyrophosphatase and galactosyltransferase activities were solubilized by deoxycholate and the membrane pellets remaining after solubilization still retained some galactosyltransferase activity which was stimulated by Cytidine 5′-diphosphate-choline. In different membrane fractions a concerted effect of both uridine diphosphate-galactose pyrophosphatase and glycoprotein:galactosyltransferase enzymes on the substrate uridine diphosphate-galactose is indicated and their eventual controlling effects on the glycopolymer synthesis in vitro or in vivo need careful evaluation.
Alberth H. Van Gennip - One of the best experts on this subject based on the ideXlab platform.
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the roles of uridine Cytidine kinase and ctp synthetase in the synthesis of ctp in malignant human t lymphocytic cells
Advances in Experimental Medicine and Biology, 1995Co-Authors: A A Van Den Berg, H. Van Lenthe, Andre B P Van Kuilenburg, Alberth H. Van GennipAbstract:In human T-lymphocytic cells pyrimidine ribonucleotides are predominantly synthesized via the salvage pathways [1, 2]. Cytosine ribonucleotides can be synthesized by salvage of Cytidine or through the salvage of uridine and subsequent conversion of UTP into CTP by the action of CTP synthetase (E.C. 6.3.4.2.). Uridine and Cytidine are competing substrates for uridine/Cytidine kinase (urd/cyd kinase, EC 2.7.1.48) [3]. Before, we demonstrated increased CTP pools in human lymphocytic leukemia blasts and MOLT-3 T-ALL cell-line cells as well as in proliferating normal human T-lymphocytic cells in comparison with resting human peripheral blood lymphocytes [1, 4]. At physiological concentrations of uridine and Cytidine, in the MOLT-3 cells this increase correlates with an increased activity of CTP synthetase [4]. For benign proliferating human T lymphocytes a similar increase in cytosine ribonucleotides as in MOLT-3 cells was found. However, CTP synthetase contributes less to this pool compared to the enzyme in the MOLT-3 cells [4, 5]. Therefore, we hypothesized that Cytidine is more avidly converted into CTP in the normal T lymphocytes, compared to the MOLT-3 cells at physiological concentrations of uridine and Cytidine.
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the roles of uridine Cytidine kinase and ctp synthetase in the synthesis of ctp in malignant human t lymphocytic cells
Leukemia, 1994Co-Authors: A A Van Den Berg, Sandra Busch, H. Van Lenthe, Dirk De Korte, Alberth H. Van GennipAbstract:The pattern of incorporation of [14C]uridine showed that in MOLT-3 cells an increased proportion of CTP was synthesized via CTP synthetase, compared to proliferating normal human T lymphocytes at a physiological concentration of Cytidine ( <0.5 microM). Furthermore, in the proliferating normal human T lymphocytes similar patterns of incorporation of [14C]uridine were observed in the presence of the physiological concentration of Cytidine and after addition of 2 microM of Cytidine. In contrast, in the MOLT-3 cells after addition of 2 microM of Cytidine the proportion of CTP synthesized by conversion of UTP into CTP was substantially decreased, whereas the salvage of Cytidine was proportionally increased. We conclude that the reutilization of uridine is a preferred route in the synthesis of CTP for MOLT-3 cells at physiological concentrations of uridine and Cytidine, whereas in proliferating normal human T lymphocytes CTP is largely synthesized through reutilization of Cytidine. This difference in salvage of pyrimidine ribonucleosides may be exploited for selective chemotherapy
Sailen Mookerjea - One of the best experts on this subject based on the ideXlab platform.
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Studies on uridine diphosphate-galactose pyrophosphatase and uridine diphosphate-galactose: glycoprotein galactosyltransferase activities in microsomal membranes.
Archives of Biochemistry and Biophysics, 2004Co-Authors: Sailen Mookerjea, James W.m. YungAbstract:Abstract Rat liver microsomes showed very active uridine diphosphate-galactose pyrophosphatase activity leading to the hydrolysis of uridine diphosphate-galactose into galactose1-phosphate and finally into galactose. The activity was observed in presence of buffers with wide ranges of pH. Different concentrations of divalent cations, such as Mn 2+ , Mg 2+ , and Ca 2+ had no significant effect on the enzyme activity. A number of nucleotides and their derivatives inhibited the pyrophosphatase activity. Of these, different concentrations of uridine monophosphate, Cytidine 5′-phosphate and Cytidine 5′-diphosphate have slight or no effect; Cytidine 5′-triphosphate, adenosine 5′-triphosphate, guanosine 5′-triphosphate, Cytidine 5′-diphosphate-glucose and guanosine 5′-diphosphate-glucose showed strong inhibitory effect whereas Cytidine 5′-diphosphate-choline showed a moderate effect on the pyrophosphatase. All these nucleotides also showed variable stimulatory effects on uridine diphosphate-galactose:glycoprotein galactosyltransferase activity in the microsomes which could be partly related to their inhibitory effects on uridine diphosphate-galactose pyrophosphatase. Among them uridine monophosphate, Cytidine 5′-phosphate, and Cytidine 5′-diphosphate stimulated galactosyltransferase activity without showing appreciable inhibition of pyrophosphatase, Cytidine 5′-diphosphate-choline, although did not inhibit pyrophosphatase as effectively as Cytidine 5′-triphosphate, guanosine 5′-triphosphate, adenosine 5′-triphosphate, Cytidine 5′-diphosphate-glucose, and guanosine 5′-diphosphate-glucose but stimulated galactosyltransferase activity as well as those. The fact that Cytidine 5′-diphosphate-choline stimulated galactosyltransferase more effectively than Cytidine 5′-phosphate, Cytidine 5′-diphosphate, and Cytidine 5′-triphosphate suggested an additional role of the choline moiety in the system. It has been also shown that Cytidine 5′-diphosphate-choline can affect the saturation of galactosyltransferase enzyme at a much lower concentration of uridine diphosphate-galactose. Most of the pyrophosphatase and galactosyltransferase activities were solubilized by deoxycholate and the membrane pellets remaining after solubilization still retained some galactosyltransferase activity which was stimulated by Cytidine 5′-diphosphate-choline. In different membrane fractions a concerted effect of both uridine diphosphate-galactose pyrophosphatase and glycoprotein:galactosyltransferase enzymes on the substrate uridine diphosphate-galactose is indicated and their eventual controlling effects on the glycopolymer synthesis in vitro or in vivo need careful evaluation.
Bora E Baysal - One of the best experts on this subject based on the ideXlab platform.
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apobec3a Cytidine deaminase induces rna editing in monocytes and macrophages
Nature Communications, 2015Co-Authors: Shraddha Sharma, Santosh K Patnaik, Thomas R Taggart, Eric Kannisto, Sally M Enriquez, Paul Gollnick, Bora E BaysalAbstract:The extent, regulation and enzymatic basis of RNA editing by Cytidine deamination are incompletely understood. Here we show that transcripts of hundreds of genes undergo site-specific C>U RNA editing in macrophages during M1 polarization and in monocytes in response to hypoxia and interferons. This editing alters the amino acid sequences for scores of proteins, including many that are involved in pathogenesis of viral diseases. APOBEC3A, which is known to deaminate Cytidines of single-stranded DNA and to inhibit viruses and retrotransposons, mediates this RNA editing. Amino acid residues of APOBEC3A that are known to be required for its DNA deamination and anti-retrotransposition activities were also found to affect its RNA deamination activity. Our study demonstrates the cellular RNA editing activity of a member of the APOBEC3 family of innate restriction factors and expands the understanding of C>U RNA editing in mammals.
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APOBEC3A Cytidine deaminase induces RNA editing in monocytes and macrophages
Nature Communications, 2015Co-Authors: Shraddha Sharma, Santosh K Patnaik, Eric Kannisto, Sally M Enriquez, Paul Gollnick, R. Thomas Taggart, Bora E BaysalAbstract:The extent, regulation and enzymatic basis of RNA editing by Cytidine deamination are incompletely understood. Here we show that transcripts of hundreds of genes undergo site-specific C>U RNA editing in macrophages during M1 polarization and in monocytes in response to hypoxia and interferons. This editing alters the amino acid sequences for scores of proteins, including many that are involved in pathogenesis of viral diseases. APOBEC3A, which is known to deaminate Cytidines of single-stranded DNA and to inhibit viruses and retrotransposons, mediates this RNA editing. Amino acid residues of APOBEC3A that are known to be required for its DNA deamination and anti-retrotransposition activities were also found to affect its RNA deamination activity. Our study demonstrates the cellular RNA editing activity of a member of the APOBEC3 family of innate restriction factors and expands the understanding of C>U RNA editing in mammals. Aberrant RNA editing is linked to a range of neuropsychiatric and chronic diseases. Here Sharma et al . show that APOBEC3A can function as an RNA editing protein in response to physiological stimuli, significantly expanding our understanding of RNA editing and the role this may play in diseases.
Ian Small - One of the best experts on this subject based on the ideXlab platform.
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The Cytidine deaminase signature HxE(x)(n)CxxC of DYW1 binds zinc and is necessary for RNA editing of ndhD-1
New Phytologist, 2014Co-Authors: Clement Boussardon, Alexandra Avon, Peter Kindgren, Charles S. Bond, Michael Challenor, Claire Lurin, Ian SmallAbstract:In flowering plants, RNA editing involves deamination of specific Cytidines to uridines in both mitochondrial and chloroplast transcripts. Pentatricopeptide repeat (PPR) proteins and multiple organellar RNA editing factor (MORF) proteins have been shown to be involved in RNA editing but none have been shown to possess Cytidine deaminase activity. The DYW domain of some PPR proteins contains a highly conserved signature resembling the zinc-binding active site motif of known nucleotide deaminases. We modified these highly conserved amino acids in the DYW motif of DYW1, an editing factor required for editing of the ndhD-1 site in Arabidopsis chloroplasts. We demonstrate that several amino acids of this signature motif are required for RNA editing in vivo and for zinc binding in vitro. We conclude that the DYW domain of DYW1 has features in common with Cytidine deaminases, reinforcing the hypothesis that this domain forms part of the active enzyme that carries out RNA editing in plants.
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a hypothesis on the identification of the editing enzyme in plant organelles
FEBS Letters, 2007Co-Authors: Veronique Salone, Ian Small, Mareike Rudinger, Monika Polsakiewicz, Beate Hoffmann, Milena Grothmalonek, Boris Szurek, Volker Knoop, Claire LurinAbstract:RNA editing in plant organelles is an enigmatic process leading to conversion of Cytidines into uridines. Editing specificity is determined by proteins; both those known so far are pentatricopeptide repeat (PPR) proteins. The enzyme catalysing RNA editing in plants is still totally unknown. We propose that the DYW domain found in many higher plant PPR proteins is the missing catalytic domain. This hypothesis is based on two compelling observations: (i) the DYW domain contains invariant residues that match the active site of Cytidine deaminases; (ii) the phylogenetic distribution of the DYW domain is strictly correlated with RNA editing.
