The Experts below are selected from a list of 66 Experts worldwide ranked by ideXlab platform
Edward P Whitehead - One of the best experts on this subject based on the ideXlab platform.
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interaction of the high affinity inhibitor tetrahydro dump with the allosteric enzyme deoxycytidylate Aminohydrolase
Archives of Biochemistry and Biophysics, 1994Co-Authors: Roberto Nucci, Carlo Vaccaro, Mosè Rossi, Ferdinando Febbraio, Gennaro Piccialli, L Denapoli, Edward P WhiteheadAbstract:Abstract Tetrahydro-dUMP, an analog of the putative transition state in aminohydrolysis of deoxycytidine monophosphate (dCMP) inhibits the allosteric enzyme deoxycytidylate Aminohydrolase with high affinity. The inhibition is reversible, and its kinetics is consistent with the analog binding at the substrate site only to one and the same conformation that binds the substrate dCMP. Such kinetics is what would be expected for a transition state analog interacting in an allosteric "K system."
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allosteric modifier and substrate binding of donkey deoxycytidylate Aminohydrolase ec 3 5 4 12
Archives of Biochemistry and Biophysics, 1991Co-Authors: Roberto Nucci, Carlo Vaccaro, Mosè Rossi, Carlo A. Raia, Edward P WhiteheadAbstract:Abstract The hexameric allosteric enzyme deoxycytidylate Aminohydrolase from donkey spleen is shown by equilibrium dialysis to bind specifically the allosteric inhibitor, dTTP, the activator dCTP, and the substrate analog dAMP each at six sites (the dTTP and dCTP sites may or may not be identical). These conclusions contrast with earlier ones that there were four sites for each effector; reasons for the discrepancy are discussed. With the knowledge of site numbers and the kinetic information from the accompanying paper it is concluded that the kinetic cooperativity of the enzyme excludes a concerted conformational transition mechanism. Amino acid analysis gives a molecular weight of 18,842 Da per subunit, i.e., 113,052 for the hexamer. A new simplified purification of homogeneous enzyme from donkey spleen probably useful for dCMP Aminohydrolase from other sources is described.
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hill coefficient ratios give binding ratios of allosteric enzyme effectors inhibition activation and squatting in deoxycytidylate Aminohydrolase ec 3 5 4 12
Archives of Biochemistry and Biophysics, 1991Co-Authors: Edward P Whitehead, Carlo Vaccaro, Roberto Nucci, Mosè RossiAbstract:Abstract The ratio of the steady-state kinetic Hill coefficients of two different effectors equals (under some rather weak general assumptions) the ratio in which the effectors displace each other from an enzyme. This principle can make implications of experimental allosteric enzyme kinetic data immediately apparent. We can use it to find that one molecule of the allosteric inhibitor of dCMP Aminohydrolase, at moderately high effector concentrations, displaces one molecule of substrate, or one molecule of activator, whereas at very high concentrations, one molecule of inhibitor displaces two of substrate. Further use of the principle suggests that substrate, at high concentrations, binds to activator sites. However, ratios of substrate, activator, and inhibitor Hill coefficients are incompatible with a simple model of activation in which substrate and activator are bound to the same conformation.
Mosè Rossi - One of the best experts on this subject based on the ideXlab platform.
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interaction of the high affinity inhibitor tetrahydro dump with the allosteric enzyme deoxycytidylate Aminohydrolase
Archives of Biochemistry and Biophysics, 1994Co-Authors: Roberto Nucci, Carlo Vaccaro, Mosè Rossi, Ferdinando Febbraio, Gennaro Piccialli, L Denapoli, Edward P WhiteheadAbstract:Abstract Tetrahydro-dUMP, an analog of the putative transition state in aminohydrolysis of deoxycytidine monophosphate (dCMP) inhibits the allosteric enzyme deoxycytidylate Aminohydrolase with high affinity. The inhibition is reversible, and its kinetics is consistent with the analog binding at the substrate site only to one and the same conformation that binds the substrate dCMP. Such kinetics is what would be expected for a transition state analog interacting in an allosteric "K system."
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allosteric modifier and substrate binding of donkey deoxycytidylate Aminohydrolase ec 3 5 4 12
Archives of Biochemistry and Biophysics, 1991Co-Authors: Roberto Nucci, Carlo Vaccaro, Mosè Rossi, Carlo A. Raia, Edward P WhiteheadAbstract:Abstract The hexameric allosteric enzyme deoxycytidylate Aminohydrolase from donkey spleen is shown by equilibrium dialysis to bind specifically the allosteric inhibitor, dTTP, the activator dCTP, and the substrate analog dAMP each at six sites (the dTTP and dCTP sites may or may not be identical). These conclusions contrast with earlier ones that there were four sites for each effector; reasons for the discrepancy are discussed. With the knowledge of site numbers and the kinetic information from the accompanying paper it is concluded that the kinetic cooperativity of the enzyme excludes a concerted conformational transition mechanism. Amino acid analysis gives a molecular weight of 18,842 Da per subunit, i.e., 113,052 for the hexamer. A new simplified purification of homogeneous enzyme from donkey spleen probably useful for dCMP Aminohydrolase from other sources is described.
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hill coefficient ratios give binding ratios of allosteric enzyme effectors inhibition activation and squatting in deoxycytidylate Aminohydrolase ec 3 5 4 12
Archives of Biochemistry and Biophysics, 1991Co-Authors: Edward P Whitehead, Carlo Vaccaro, Roberto Nucci, Mosè RossiAbstract:Abstract The ratio of the steady-state kinetic Hill coefficients of two different effectors equals (under some rather weak general assumptions) the ratio in which the effectors displace each other from an enzyme. This principle can make implications of experimental allosteric enzyme kinetic data immediately apparent. We can use it to find that one molecule of the allosteric inhibitor of dCMP Aminohydrolase, at moderately high effector concentrations, displaces one molecule of substrate, or one molecule of activator, whereas at very high concentrations, one molecule of inhibitor displaces two of substrate. Further use of the principle suggests that substrate, at high concentrations, binds to activator sites. However, ratios of substrate, activator, and inhibitor Hill coefficients are incompatible with a simple model of activation in which substrate and activator are bound to the same conformation.
Roberto Nucci - One of the best experts on this subject based on the ideXlab platform.
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interaction of the high affinity inhibitor tetrahydro dump with the allosteric enzyme deoxycytidylate Aminohydrolase
Archives of Biochemistry and Biophysics, 1994Co-Authors: Roberto Nucci, Carlo Vaccaro, Mosè Rossi, Ferdinando Febbraio, Gennaro Piccialli, L Denapoli, Edward P WhiteheadAbstract:Abstract Tetrahydro-dUMP, an analog of the putative transition state in aminohydrolysis of deoxycytidine monophosphate (dCMP) inhibits the allosteric enzyme deoxycytidylate Aminohydrolase with high affinity. The inhibition is reversible, and its kinetics is consistent with the analog binding at the substrate site only to one and the same conformation that binds the substrate dCMP. Such kinetics is what would be expected for a transition state analog interacting in an allosteric "K system."
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allosteric modifier and substrate binding of donkey deoxycytidylate Aminohydrolase ec 3 5 4 12
Archives of Biochemistry and Biophysics, 1991Co-Authors: Roberto Nucci, Carlo Vaccaro, Mosè Rossi, Carlo A. Raia, Edward P WhiteheadAbstract:Abstract The hexameric allosteric enzyme deoxycytidylate Aminohydrolase from donkey spleen is shown by equilibrium dialysis to bind specifically the allosteric inhibitor, dTTP, the activator dCTP, and the substrate analog dAMP each at six sites (the dTTP and dCTP sites may or may not be identical). These conclusions contrast with earlier ones that there were four sites for each effector; reasons for the discrepancy are discussed. With the knowledge of site numbers and the kinetic information from the accompanying paper it is concluded that the kinetic cooperativity of the enzyme excludes a concerted conformational transition mechanism. Amino acid analysis gives a molecular weight of 18,842 Da per subunit, i.e., 113,052 for the hexamer. A new simplified purification of homogeneous enzyme from donkey spleen probably useful for dCMP Aminohydrolase from other sources is described.
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hill coefficient ratios give binding ratios of allosteric enzyme effectors inhibition activation and squatting in deoxycytidylate Aminohydrolase ec 3 5 4 12
Archives of Biochemistry and Biophysics, 1991Co-Authors: Edward P Whitehead, Carlo Vaccaro, Roberto Nucci, Mosè RossiAbstract:Abstract The ratio of the steady-state kinetic Hill coefficients of two different effectors equals (under some rather weak general assumptions) the ratio in which the effectors displace each other from an enzyme. This principle can make implications of experimental allosteric enzyme kinetic data immediately apparent. We can use it to find that one molecule of the allosteric inhibitor of dCMP Aminohydrolase, at moderately high effector concentrations, displaces one molecule of substrate, or one molecule of activator, whereas at very high concentrations, one molecule of inhibitor displaces two of substrate. Further use of the principle suggests that substrate, at high concentrations, binds to activator sites. However, ratios of substrate, activator, and inhibitor Hill coefficients are incompatible with a simple model of activation in which substrate and activator are bound to the same conformation.
Carlo Vaccaro - One of the best experts on this subject based on the ideXlab platform.
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interaction of the high affinity inhibitor tetrahydro dump with the allosteric enzyme deoxycytidylate Aminohydrolase
Archives of Biochemistry and Biophysics, 1994Co-Authors: Roberto Nucci, Carlo Vaccaro, Mosè Rossi, Ferdinando Febbraio, Gennaro Piccialli, L Denapoli, Edward P WhiteheadAbstract:Abstract Tetrahydro-dUMP, an analog of the putative transition state in aminohydrolysis of deoxycytidine monophosphate (dCMP) inhibits the allosteric enzyme deoxycytidylate Aminohydrolase with high affinity. The inhibition is reversible, and its kinetics is consistent with the analog binding at the substrate site only to one and the same conformation that binds the substrate dCMP. Such kinetics is what would be expected for a transition state analog interacting in an allosteric "K system."
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allosteric modifier and substrate binding of donkey deoxycytidylate Aminohydrolase ec 3 5 4 12
Archives of Biochemistry and Biophysics, 1991Co-Authors: Roberto Nucci, Carlo Vaccaro, Mosè Rossi, Carlo A. Raia, Edward P WhiteheadAbstract:Abstract The hexameric allosteric enzyme deoxycytidylate Aminohydrolase from donkey spleen is shown by equilibrium dialysis to bind specifically the allosteric inhibitor, dTTP, the activator dCTP, and the substrate analog dAMP each at six sites (the dTTP and dCTP sites may or may not be identical). These conclusions contrast with earlier ones that there were four sites for each effector; reasons for the discrepancy are discussed. With the knowledge of site numbers and the kinetic information from the accompanying paper it is concluded that the kinetic cooperativity of the enzyme excludes a concerted conformational transition mechanism. Amino acid analysis gives a molecular weight of 18,842 Da per subunit, i.e., 113,052 for the hexamer. A new simplified purification of homogeneous enzyme from donkey spleen probably useful for dCMP Aminohydrolase from other sources is described.
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hill coefficient ratios give binding ratios of allosteric enzyme effectors inhibition activation and squatting in deoxycytidylate Aminohydrolase ec 3 5 4 12
Archives of Biochemistry and Biophysics, 1991Co-Authors: Edward P Whitehead, Carlo Vaccaro, Roberto Nucci, Mosè RossiAbstract:Abstract The ratio of the steady-state kinetic Hill coefficients of two different effectors equals (under some rather weak general assumptions) the ratio in which the effectors displace each other from an enzyme. This principle can make implications of experimental allosteric enzyme kinetic data immediately apparent. We can use it to find that one molecule of the allosteric inhibitor of dCMP Aminohydrolase, at moderately high effector concentrations, displaces one molecule of substrate, or one molecule of activator, whereas at very high concentrations, one molecule of inhibitor displaces two of substrate. Further use of the principle suggests that substrate, at high concentrations, binds to activator sites. However, ratios of substrate, activator, and inhibitor Hill coefficients are incompatible with a simple model of activation in which substrate and activator are bound to the same conformation.
Clauspeter Witte - One of the best experts on this subject based on the ideXlab platform.
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the ureide degrading reactions of purine ring catabolism employ three amidohydrolases and one Aminohydrolase in arabidopsis soybean and rice
Plant Physiology, 2013Co-Authors: Andrea K Werner, Nieves Medinaescobar, Monika Zulawski, Imogen Sparkes, Clauspeter WitteAbstract:Several ureides are intermediates of purine base catabolism, releasing nitrogen from the purine nucleotides for reassimilation into amino acids. In some legumes like soybean (Glycine max), ureides are used for nodule-to-shoot translocation of fixed nitrogen. Four enzymes of Arabidopsis (Arabidopsis thaliana), (1) allantoinase, (2) allantoate amidohydrolase (AAH), (3) ureidoglycine Aminohydrolase, and (4) ureidoglycolate amidohydrolase (UAH), catalyze the complete hydrolysis of the ureide allantoin in vitro. However, the metabolic route in vivo remains controversial. Here, in growth and metabolite analyses of Arabidopsis mutants, we demonstrate that these enzymes are required for allantoin degradation in vivo. Orthologous enzymes are present in soybean, encoded by one to four gene copies. All isoenzymes are active in vitro, while some may be inefficiently translated in vivo. Surprisingly, transcript and protein amounts are not significantly regulated by nitrogen fixation or leaf ureide content. A requirement for soybean AAH and UAH for ureide catabolism in leaves has been demonstrated by the use of virus-induced gene silencing. Functional AAH, ureidoglycine Aminohydrolase, and UAH are also present in rice (Oryza sativa), and orthologous genes occur in all other plant genomes sequenced to date, indicating that the amidohydrolase route of ureide degradation is universal in plants, including mosses (e.g. Physcomitrella patens) and algae (e.g. Chlamydomomas reinhardtii).
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Ureide catabolism in Arabidopsis thaliana and Escherichia coli
Nature Chemical Biology, 2010Co-Authors: Andrea K Werner, Tina Romeis, Clauspeter WitteAbstract:The availability of whole genome sequences boosts the identification of biochemical pathways conserved across species using tools of comparative genomics. A cross-organism protein association analysis allowed us to identify two enzymes, ureidoglycine Aminohydrolase and ureidoglycolate amidohydrolase, that catalyze the final reactions of purine degradation in the model plant Arabidopsis thaliana . A similar pathway was found in Escherichia coli , while an alternative metabolic route via ureidoglycine transaminase can be predicted for other organisms. Allantoin catabolism provides nitrogen, carbon and energy for several species, but the biochemical route to these resources in some species was unclear. A multidimensional bioinformatic search across organisms has now led to the identification of two enzymes that complete the degradation pathway.