The Experts below are selected from a list of 327 Experts worldwide ranked by ideXlab platform

Kerry S. Smith - One of the best experts on this subject based on the ideXlab platform.

  • Allosteric Regulation of lactobacillus plantarum xylulose 5 phosphate fructose 6 phosphate phosphoketolase xfp
    Journal of Bacteriology, 2015
    Co-Authors: Katie Glenn, Kerry S. Smith
    Abstract:

    ABSTRACT Xylulose 5-phosphate/fructose 6-phosphate phosphoketolase (Xfp), which catalyzes the conversion of xylulose 5-phosphate (X5P) or fructose 6-phosphate (F6P) to acetyl phosphate, plays a key role in carbohydrate metabolism in a number of bacteria. Recently, we demonstrated that the fungal Cryptococcus neoformans Xfp2 exhibits both substrate cooperativity for all substrates (X5P, F6P, and P i ) and Allosteric Regulation in the forms of inhibition by phosphoenolpyruvate (PEP), oxaloacetic acid (OAA), and ATP and activation by AMP (K. Glenn, C. Ingram-Smith, and K. S. Smith. Eukaryot Cell 13: 657–663, 2014). Allosteric Regulation has not been reported previously for the characterized bacterial Xfps. Here, we report the discovery of substrate cooperativity and Allosteric Regulation among bacterial Xfps, specifically the Lactobacillus plantarum Xfp. L. plantarum Xfp is an Allosteric enzyme inhibited by PEP, OAA, and glyoxylate but unaffected by the presence of ATP or AMP. Glyoxylate is an additional inhibitor to those previously reported for C. neoformans Xfp2. As with C. neoformans Xfp2, PEP and OAA share the same or possess overlapping sites on L. plantarum Xfp. Glyoxylate, which had the lowest half-maximal inhibitory concentration of the three inhibitors, binds at a separate site. This study demonstrates that substrate cooperativity and Allosteric Regulation may be common properties among bacterial and eukaryotic Xfp enzymes, yet important differences exist between the enzymes in these two domains. IMPORTANCE Xylulose 5-phosphate/fructose 6-phosphate phosphoketolase (Xfp) plays a key role in carbohydrate metabolism in a number of bacteria. Although we recently demonstrated that the fungal Cryptococcus Xfp is subject to substrate cooperativity and Allosteric Regulation, neither phenomenon has been reported for a bacterial Xfp. Here, we report that the Lactobacillus plantarum Xfp displays substrate cooperativity and is Allosterically inhibited by phosphoenolpyruvate and oxaloacetate, as is the case for Cryptococcus Xfp. The bacterial enzyme is unaffected by the presence of AMP or ATP, which act as a potent activator and inhibitor of the fungal Xfp, respectively. Our results demonstrate that substrate cooperativity and Allosteric Regulation may be common properties among bacterial and eukaryotic Xfps, yet important differences exist between the enzymes in these two domains.

  • Allosteric Regulation of Lactobacillus plantarum Xylulose 5-Phosphate/Fructose 6-Phosphate Phosphoketolase (Xfp)
    Journal of Bacteriology, 2015
    Co-Authors: Katie Glenn, Kerry S. Smith
    Abstract:

    Xylulose 5-phosphate/fructose 6-phosphate phosphoketolase (Xfp), which catalyzes the conversion of xylulose 5-phosphate (X5P) or fructose 6-phosphate (F6P) to acetyl phosphate, plays a key role in carbohydrate metabolism in a number of bacteria. Recently, we demonstrated that the fungal Cryptococcus neoformans Xfp2 exhibits both substrate cooperativity for all substrates (X5P, F6P, and P i ) and Allosteric Regulation in the forms of inhibition by phosphoenolpyruvate (PEP), oxaloacetic acid (OAA), and ATP and activation by AMP (K. Glenn, C. Ingram-Smith, and K. S. Smith. Eukaryot Cell 13: 657–663, 2014). Allosteric Regulation has not been reported previously for the characterized bacterial Xfps. Here, we report the discovery of substrate cooperativity and Allosteric Regulation among bacterial Xfps, specifically the Lactobacillus plantarum Xfp. L. plantarum Xfp is an Allosteric enzyme inhibited by PEP, OAA, and glyoxylate but unaffected by the presence of ATP or AMP. Glyoxylate is an additional inhibitor to those previously reported for C. neoformans Xfp2. As with C. neoformans Xfp2, PEP and OAA share the same or possess overlapping sites on L. plantarum Xfp. Glyoxylate, which had the lowest half-maximal inhibitory concentration of the three inhibitors, binds at a separate site. This study demonstrates that substrate cooperativity and Allosteric Regulation may be common properties among bacterial and eukaryotic Xfp enzymes, yet important differences exist between the enzymes in these two domains. IMPORTANCE Xylulose 5-phosphate/fructose 6-phosphate phosphoketolase (Xfp) plays a key role in carbohydrate metabolism in a number of bacteria. Although we recently demonstrated that the fungal Cryptococcus Xfp is subject to substrate cooperativity and Allosteric Regulation, neither phenomenon has been reported for a bacterial Xfp. Here, we report that the Lactobacillus plantarum Xfp displays substrate cooperativity and is Allosterically inhibited by phosphoenolpyruvate and oxaloacetate, as is the case for Cryptococcus Xfp. The bacterial enzyme is unaffected by the presence of AMP or ATP, which act as a potent activator and inhibitor of the fungal Xfp, respectively. Our results demonstrate that substrate cooperativity and Allosteric Regulation may be common properties among bacterial and eukaryotic Xfps, yet important differences exist between the enzymes in these two domains.

Katie Glenn - One of the best experts on this subject based on the ideXlab platform.

  • Allosteric Regulation of lactobacillus plantarum xylulose 5 phosphate fructose 6 phosphate phosphoketolase xfp
    Journal of Bacteriology, 2015
    Co-Authors: Katie Glenn, Kerry S. Smith
    Abstract:

    ABSTRACT Xylulose 5-phosphate/fructose 6-phosphate phosphoketolase (Xfp), which catalyzes the conversion of xylulose 5-phosphate (X5P) or fructose 6-phosphate (F6P) to acetyl phosphate, plays a key role in carbohydrate metabolism in a number of bacteria. Recently, we demonstrated that the fungal Cryptococcus neoformans Xfp2 exhibits both substrate cooperativity for all substrates (X5P, F6P, and P i ) and Allosteric Regulation in the forms of inhibition by phosphoenolpyruvate (PEP), oxaloacetic acid (OAA), and ATP and activation by AMP (K. Glenn, C. Ingram-Smith, and K. S. Smith. Eukaryot Cell 13: 657–663, 2014). Allosteric Regulation has not been reported previously for the characterized bacterial Xfps. Here, we report the discovery of substrate cooperativity and Allosteric Regulation among bacterial Xfps, specifically the Lactobacillus plantarum Xfp. L. plantarum Xfp is an Allosteric enzyme inhibited by PEP, OAA, and glyoxylate but unaffected by the presence of ATP or AMP. Glyoxylate is an additional inhibitor to those previously reported for C. neoformans Xfp2. As with C. neoformans Xfp2, PEP and OAA share the same or possess overlapping sites on L. plantarum Xfp. Glyoxylate, which had the lowest half-maximal inhibitory concentration of the three inhibitors, binds at a separate site. This study demonstrates that substrate cooperativity and Allosteric Regulation may be common properties among bacterial and eukaryotic Xfp enzymes, yet important differences exist between the enzymes in these two domains. IMPORTANCE Xylulose 5-phosphate/fructose 6-phosphate phosphoketolase (Xfp) plays a key role in carbohydrate metabolism in a number of bacteria. Although we recently demonstrated that the fungal Cryptococcus Xfp is subject to substrate cooperativity and Allosteric Regulation, neither phenomenon has been reported for a bacterial Xfp. Here, we report that the Lactobacillus plantarum Xfp displays substrate cooperativity and is Allosterically inhibited by phosphoenolpyruvate and oxaloacetate, as is the case for Cryptococcus Xfp. The bacterial enzyme is unaffected by the presence of AMP or ATP, which act as a potent activator and inhibitor of the fungal Xfp, respectively. Our results demonstrate that substrate cooperativity and Allosteric Regulation may be common properties among bacterial and eukaryotic Xfps, yet important differences exist between the enzymes in these two domains.

  • Allosteric Regulation of Lactobacillus plantarum Xylulose 5-Phosphate/Fructose 6-Phosphate Phosphoketolase (Xfp)
    Journal of Bacteriology, 2015
    Co-Authors: Katie Glenn, Kerry S. Smith
    Abstract:

    Xylulose 5-phosphate/fructose 6-phosphate phosphoketolase (Xfp), which catalyzes the conversion of xylulose 5-phosphate (X5P) or fructose 6-phosphate (F6P) to acetyl phosphate, plays a key role in carbohydrate metabolism in a number of bacteria. Recently, we demonstrated that the fungal Cryptococcus neoformans Xfp2 exhibits both substrate cooperativity for all substrates (X5P, F6P, and P i ) and Allosteric Regulation in the forms of inhibition by phosphoenolpyruvate (PEP), oxaloacetic acid (OAA), and ATP and activation by AMP (K. Glenn, C. Ingram-Smith, and K. S. Smith. Eukaryot Cell 13: 657–663, 2014). Allosteric Regulation has not been reported previously for the characterized bacterial Xfps. Here, we report the discovery of substrate cooperativity and Allosteric Regulation among bacterial Xfps, specifically the Lactobacillus plantarum Xfp. L. plantarum Xfp is an Allosteric enzyme inhibited by PEP, OAA, and glyoxylate but unaffected by the presence of ATP or AMP. Glyoxylate is an additional inhibitor to those previously reported for C. neoformans Xfp2. As with C. neoformans Xfp2, PEP and OAA share the same or possess overlapping sites on L. plantarum Xfp. Glyoxylate, which had the lowest half-maximal inhibitory concentration of the three inhibitors, binds at a separate site. This study demonstrates that substrate cooperativity and Allosteric Regulation may be common properties among bacterial and eukaryotic Xfp enzymes, yet important differences exist between the enzymes in these two domains. IMPORTANCE Xylulose 5-phosphate/fructose 6-phosphate phosphoketolase (Xfp) plays a key role in carbohydrate metabolism in a number of bacteria. Although we recently demonstrated that the fungal Cryptococcus Xfp is subject to substrate cooperativity and Allosteric Regulation, neither phenomenon has been reported for a bacterial Xfp. Here, we report that the Lactobacillus plantarum Xfp displays substrate cooperativity and is Allosterically inhibited by phosphoenolpyruvate and oxaloacetate, as is the case for Cryptococcus Xfp. The bacterial enzyme is unaffected by the presence of AMP or ATP, which act as a potent activator and inhibitor of the fungal Xfp, respectively. Our results demonstrate that substrate cooperativity and Allosteric Regulation may be common properties among bacterial and eukaryotic Xfps, yet important differences exist between the enzymes in these two domains.

Andrea Mozzarelli - One of the best experts on this subject based on the ideXlab platform.

  • The molecular pathway for the Allosteric Regulation of tryptophan synthase.
    Biochimica et biophysica acta, 2003
    Co-Authors: Samanta Raboni, Stefano Bettati, Barbara Pioselli, Andrea Mozzarelli
    Abstract:

    The pyridoxal 5'-phosphate (PLP)-dependent tryptophan synthase is a alpha(2)beta(2) complex. The alpha-beta subunit interaction plays a critical role both in the reciprocal activation of the individual subunits and in the Allosteric Regulation. We have investigated whether mutations of alpha loop6 Gly(181) and beta helix6 Ser(178) affect intersubunit communication. The loss of the hydrogen bond between these residues, achieved by proline substitution, does not significantly influence the intersubunit catalytic activation, but completely abolishes ligand-induced intersubunit signaling. The comparison of the crystal structure of the wild type and beta Ser(178)Pro mutant, in the absence and presence of alpha-subunit ligands, indicates that the removal of the interaction between beta Ser(178) and alpha Gly(181) strongly affects the equilibrium between active (closed) and inactive (open) conformations of the alpha-active site, the latter being stabilized in both mutants.

  • The molecular pathway for the Allosteric Regulation of tryptophan synthase.
    Biochimica et Biophysica Acta, 2003
    Co-Authors: Samanta Raboni, Stefano Bettati, Barbara Pioselli, Andrea Mozzarelli
    Abstract:

    Abstract The pyridoxal 5′-phosphate (PLP)-dependent tryptophan synthase is a α 2 β 2 complex. The α−β subunit interaction plays a critical role both in the reciprocal activation of the individual subunits and in the Allosteric Regulation. We have investigated whether mutations of αloop6 Gly 181 and βhelix6 Ser 178 affect intersubunit communication. The loss of the hydrogen bond between these residues, achieved by proline substitution, does not significantly influence the intersubunit catalytic activation, but completely abolishes ligand-induced intersubunit signaling. The comparison of the crystal structure of the wild type and βSer 178 Pro mutant, in the absence and presence of α-subunit ligands, indicates that the removal of the interaction between βSer 178 and αGly 181 strongly affects the equilibrium between active (closed) and inactive (open) conformations of the α-active site, the latter being stabilized in both mutants.

Stefano Bettati - One of the best experts on this subject based on the ideXlab platform.

  • Ligand reactivity and Allosteric Regulation of hemoglobin-based oxygen carriers.
    Biochimica et biophysica acta, 2008
    Co-Authors: Luca Ronda, Stefano Bruno, Stefania Abbruzzetti, Cristiano Viappiani, Stefano Bettati
    Abstract:

    Abstract Historically, exogenous administration of hemoglobin solutions to implement the oxygen transport capacity for clinical applications suffered from dramatic drawbacks, resulting in the failure of many attempts. In the last decades, the biochemical and physiological basis responsible for the therapeutic failures has been extensively investigated. It is now widely accepted that they mostly arise because, out of the confined and controlled environment of the red blood cell, hemoglobin exhibits tetramer instability, increased auto-oxidation rate, higher oxygen affinity, altered cooperativity and nitric oxide reactivity. Moreover, it became evident that the design of a hemoglobin-based oxygen carrier that exactly reproduces the “physiological” oxygen-binding curve is not only an overly ambitious task, but may also represent a wrong approach for many potential clinical applications. Under these premises, and given the complex chemical nature of blood, it is obvious that any strategy undertaken to modify the stability and function of the hemoglobin tetramer for clinical use should be driven by a detailed knowledge of its structure, dynamics and mechanism of Allosteric Regulation. We briefly review the most recent theories and experiments that increased our understanding of the mechanism of homo- and heterotropic effects in human hemoglobin, trying to interpret, on a biophysical basis, how diverse approaches like polymerization, cross-linking, site-directed mutagenesis, surface decoration and encapsulation may affect ligand affinity and Allosteric Regulation.

  • The molecular pathway for the Allosteric Regulation of tryptophan synthase.
    Biochimica et biophysica acta, 2003
    Co-Authors: Samanta Raboni, Stefano Bettati, Barbara Pioselli, Andrea Mozzarelli
    Abstract:

    The pyridoxal 5'-phosphate (PLP)-dependent tryptophan synthase is a alpha(2)beta(2) complex. The alpha-beta subunit interaction plays a critical role both in the reciprocal activation of the individual subunits and in the Allosteric Regulation. We have investigated whether mutations of alpha loop6 Gly(181) and beta helix6 Ser(178) affect intersubunit communication. The loss of the hydrogen bond between these residues, achieved by proline substitution, does not significantly influence the intersubunit catalytic activation, but completely abolishes ligand-induced intersubunit signaling. The comparison of the crystal structure of the wild type and beta Ser(178)Pro mutant, in the absence and presence of alpha-subunit ligands, indicates that the removal of the interaction between beta Ser(178) and alpha Gly(181) strongly affects the equilibrium between active (closed) and inactive (open) conformations of the alpha-active site, the latter being stabilized in both mutants.

  • The molecular pathway for the Allosteric Regulation of tryptophan synthase.
    Biochimica et Biophysica Acta, 2003
    Co-Authors: Samanta Raboni, Stefano Bettati, Barbara Pioselli, Andrea Mozzarelli
    Abstract:

    Abstract The pyridoxal 5′-phosphate (PLP)-dependent tryptophan synthase is a α 2 β 2 complex. The α−β subunit interaction plays a critical role both in the reciprocal activation of the individual subunits and in the Allosteric Regulation. We have investigated whether mutations of αloop6 Gly 181 and βhelix6 Ser 178 affect intersubunit communication. The loss of the hydrogen bond between these residues, achieved by proline substitution, does not significantly influence the intersubunit catalytic activation, but completely abolishes ligand-induced intersubunit signaling. The comparison of the crystal structure of the wild type and βSer 178 Pro mutant, in the absence and presence of α-subunit ligands, indicates that the removal of the interaction between βSer 178 and αGly 181 strongly affects the equilibrium between active (closed) and inactive (open) conformations of the α-active site, the latter being stabilized in both mutants.

Samanta Raboni - One of the best experts on this subject based on the ideXlab platform.

  • The molecular pathway for the Allosteric Regulation of tryptophan synthase.
    Biochimica et biophysica acta, 2003
    Co-Authors: Samanta Raboni, Stefano Bettati, Barbara Pioselli, Andrea Mozzarelli
    Abstract:

    The pyridoxal 5'-phosphate (PLP)-dependent tryptophan synthase is a alpha(2)beta(2) complex. The alpha-beta subunit interaction plays a critical role both in the reciprocal activation of the individual subunits and in the Allosteric Regulation. We have investigated whether mutations of alpha loop6 Gly(181) and beta helix6 Ser(178) affect intersubunit communication. The loss of the hydrogen bond between these residues, achieved by proline substitution, does not significantly influence the intersubunit catalytic activation, but completely abolishes ligand-induced intersubunit signaling. The comparison of the crystal structure of the wild type and beta Ser(178)Pro mutant, in the absence and presence of alpha-subunit ligands, indicates that the removal of the interaction between beta Ser(178) and alpha Gly(181) strongly affects the equilibrium between active (closed) and inactive (open) conformations of the alpha-active site, the latter being stabilized in both mutants.

  • The molecular pathway for the Allosteric Regulation of tryptophan synthase.
    Biochimica et Biophysica Acta, 2003
    Co-Authors: Samanta Raboni, Stefano Bettati, Barbara Pioselli, Andrea Mozzarelli
    Abstract:

    Abstract The pyridoxal 5′-phosphate (PLP)-dependent tryptophan synthase is a α 2 β 2 complex. The α−β subunit interaction plays a critical role both in the reciprocal activation of the individual subunits and in the Allosteric Regulation. We have investigated whether mutations of αloop6 Gly 181 and βhelix6 Ser 178 affect intersubunit communication. The loss of the hydrogen bond between these residues, achieved by proline substitution, does not significantly influence the intersubunit catalytic activation, but completely abolishes ligand-induced intersubunit signaling. The comparison of the crystal structure of the wild type and βSer 178 Pro mutant, in the absence and presence of α-subunit ligands, indicates that the removal of the interaction between βSer 178 and αGly 181 strongly affects the equilibrium between active (closed) and inactive (open) conformations of the α-active site, the latter being stabilized in both mutants.