The Experts below are selected from a list of 192 Experts worldwide ranked by ideXlab platform
Bruce Ganem - One of the best experts on this subject based on the ideXlab platform.
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Mapping of chorismate mutase and prephenate dehydrogenase domains in the Escherichia coli T-protein.
FEBS Journal, 2003Co-Authors: Shuqing Chen, Sarah Vincent, David Wilson, Bruce GanemAbstract:The Escherichia coli bifunctional T-protein transforms Chorismic Acid to p-hydroxyphenylpyruvic Acid in the l-tyrosine biosynthetic pathway. The 373 amino Acid T-protein is a homodimer that exhibits chorismate mutase (CM) and prephenate dehydrogenase (PDH) activities, both of which are feedback-inhibited by tyrosine. Fifteen genes coding for the T-protein and various fragments thereof were constructed and successfully expressed in order to characterize the CM, PDH and regulatory domains. Residues 1–88 constituted a functional CM domain, which was also dimeric. Both the PDH and the feedback-inhibition activities were localized in residues 94–373, but could not be separated into discrete domains. The activities of cloned CM and PDH domains were comparatively low, suggesting some cooperative interactions in the native state. Activity data further indicate that the PDH domain, in which NAD, prephenate and tyrosine binding sites were present, was more unstable than the CM domain.
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On the mechanism of chorismate mutases: Revisiting structural requirements for catalysis
Bioorganic & Medicinal Chemistry Letters, 1997Co-Authors: Christophe C Galopin, Bruce GanemAbstract:Abstract The behavior of nor-Chorismic Acid 7 has now been tested against three different chorismate mutases. Notably, 7 is not a substrate for Bacillus subtilis mutase, but is a weak competitive inhibitor (K I = 0.5 mM).
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The Mechanism of the Claisen Rearrangement: Déjà Vu All Over Again
Angewandte Chemie, 1996Co-Authors: Bruce GanemAbstract:The great baseball player Yogi Berra, who is quoted in the title, succinctly described what it meant to learn something that others had long ago appreciated. The mechanism by which the enzyme chorismate mutase accelerates the Claisen rearrangement of Chorismic Acid has for many years perplexed and intrigued chemists and biochemists. Yet classical effects of solvents and catalysts, which were largely ignored by the chemical community, not only provided important clues about the mechanism of the enzyme, but put the Claisen rearrangement in a new perspective. Whereas Chorismic Acid once seemed exceptional because it rearranged so rapidly under physiological conditions, it is now clear that even allyl vinyl ether rearranges at room temperature in aqueous solution. While the ability of the enzyme to accelerate the rearrangement of chorismate by a factor of 106 was once considered extraordinary, catalysis by trivalent aluminum compounds matches, and in some cases exceeds, those rate enhancements. Therefore, it really should not be surprising to learn that Nature has independently evolved several structurally distinct solutions to the design of enzyme catalysts for the rearrangement of Chorismic Acid.
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New insight into the catalytic mechanism of chorismate mutases from structural studies
Chemistry & Biology, 1995Co-Authors: Jon D. Stewart, Jon Clardy, Bruce GanemAbstract:Abstract Chorismate mutase catalyzes the rearrangement of Chorismic Acid to prephenic Acid, which is the first committed step in the biosynthesis of aromatic amino Acids. Its catalytic mechanism has been much studied, but is poorly understood. Recent structural information on enzymes from two species, and on an antibody that catalyzes the same reaction, has shed new light on this topic.
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synthesis of cyathiformines a c unusual fungal metabolites derived from Chorismic Acid
Tetrahedron, 1994Co-Authors: Rosemarie Meier, Bruce GanemAbstract:Abstract Expeditious syntheses of the title compounds are reported which lend credence to the apparent biogenetic relationship between the cyathiformines and (−)-Chorismic Acid.
Todd D Nelson - One of the best experts on this subject based on the ideXlab platform.
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stereocontrolled synthesis of highly functionalized cyclohexenes a short synthesis of a Chorismic Acid precursor
ChemInform, 1990Co-Authors: Gary H Posner, Todd D NelsonAbstract:The bicyclic adducts (VII), which represent rigid, highly oxygenated cyclohexenes are useful building units for the preparation of highly functionalized cyclohexenes such as (IX), (X) and (XII).
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stereocontrolled synthesis of highly functionalized cyclohexenes a short synthesis of a Chorismic Acid precursor
Tetrahedron, 1990Co-Authors: Gary H Posner, Todd D NelsonAbstract:Abstract A convenient and mild thermal procedure has been developed for stereoselective 2+4-cycloadditions of electron-rich 1,2-dioxygenated olefins 7 to electron-deficient 3-sulfonyl-2-pyrone 6 allowing isolation of the structurally and stereochemically rich initial bicyclic adducts 8. These bicyclic adducts are shown to be useful building units as exemplified by a very short and high-yield preparation of a Chorismic Acid precursor.
Jane E. Ladner - One of the best experts on this subject based on the ideXlab platform.
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Structure of isochorismate synthase in complex with magnesium
Acta Crystallographica Section D-biological Crystallography, 2008Co-Authors: James F. Parsons, Jane E. LadnerAbstract:The electron carrier menaquinone is one of many important bacterial metabolites that are derived from the key intermediate Chorismic Acid. MenF, the first enzyme in the menaquinone pathway, catalyzes the isomerization of chorismate to isochorismate. Here, an improved structure of MenF in a new crystal form is presented. The structure, solved at 2.0 A resolution in complex with magnesium, reveals a well defined closed active site. Existing evidence suggests that the mechanism of the reaction catalyzed by MenF involves nucleophilic attack of a water molecule on the chorismate ring. The structure reveals a well defined water molecule located in an appropriate position for activation by Lys190 and attack on the substrate.
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Crystal Structure of the Pyocyanin Biosynthetic Protein PhzS.
Biochemistry, 2008Co-Authors: Bryan T. Greenhagen, Asim K. Bera, Jane E. Ladner, Howard Robinson, Swarna A. Gamage, James F. ParsonsAbstract:The human pathogen Pseudomonas aeruginosa produces pyocyanin, a blue-pigmented phenazine derivative, which is known to play a role in virulence. Pyocyanin is produced from Chorismic Acid via the phenazine pathway, nine proteins encoded by a gene cluster. Phenazine-1-carboxylic Acid, the initial phenazine formed, is converted to pyocyanin in two steps that are catalyzed by the enzymes PhzM and PhzS. PhzM is an adenosylmethionine dependent methyltransferase, and PhzS is a flavin dependent hydroxylase. It has been shown that PhzM is only active in the physical presence of PhzS, suggesting that a protein−protein interaction is involved in pyocyanin formation. Such a complex would prevent the release of 5-methyl-phenazine-1-carboxylate, the putative intermediate, and an apparently unstable compound. Here, we describe the three-dimensional structure of PhzS, solved by single anomalous dispersion, at a resolution of 2.4 A. The structure reveals that PhzS is a member of the family of aromatic hydroxylases charact...
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Structural and functional analysis of the pyocyanin biosynthetic protein PhzM from Pseudomonas aeruginosa.
Biochemistry, 2007Co-Authors: James F. Parsons, Kelly Calabrese, Bryan T. Greenhagen, Howard Robinson, Jane E. LadnerAbstract:Pyocyanin is a biologically active phenazine produced by the human pathogen Pseudomonas aeruginosa. It is thought to endow P. aeruginosa with a competitive growth advantage in colonized tissue and is also thought to be a virulence factor in diseases such as cystic fibrosis and AIDS where patients are commonly infected by pathogenic Pseudomonads due to their immunocompromised state. Pyocyanin is also a chemically interesting compound due to its unusual oxidation−reduction activity. Phenazine-1-carboxylic Acid, the precursor to the bioactive phenazines, is synthesized from Chorismic Acid by enzymes encoded in a seven-gene cistron in P. aeruginosa and in other Pseudomonads. Phenzine-1-carboxylic Acid is believed to be converted to pyocyanin by the sequential actions of the putative S-adenosylmethionine-dependent N-methyltransferase PhzM and the putative flavin-dependent hydroxylase PhzS. Here we report the 1.8 A crystal structure of PhzM determined by single anomalous dispersion. Unlike many methyltransferas...
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Crystallization and X-ray diffraction analysis of salicylate synthase, a chorismate-utilizing enyme involved in siderophore biosynthesis.
Acta Crystallographica Section F-structural Biology and Crystallization Communications, 2006Co-Authors: James F. Parsons, Kelly Calabrese, Jane E. LadnerAbstract:Bacteria have evolved elaborate schemes that help them thrive in environments where free iron is severely limited. Siderophores such as yersiniabactin are small iron-scavenging molecules that are deployed by bacteria during iron starvation. Several studies have linked siderophore production and virulence. Yersiniabactin, produced by several Enterobacteriaceae, is derived from the key metabolic intermediate Chorismic Acid via its conversion to salicylate by salicylate synthase. Crystals of salicylate synthase from the uropathogen Escherichia coli CFT073 have been grown by vapour diffusion using polyethylene glycol as the precipitant. The monoclinic (P21) crystals diffract to 2.5 A. The unit-cell parameters are a = 57.27, b = 164.07, c = 59.04 A, β = 108.8°. The solvent content of the crystals is 54% and there are two molecules of the 434-amino-Acid protein in the asymmetric unit. It is anticipated that the structure will reveal key details about the reaction mechanism and the evolution of salicylate synthase.
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Crystallization and X-ray diffraction analysis of salicylate synthase, a chorismate-utilizing enyme involved in siderophore biosynthesis.
Acta crystallographica. Section F Structural biology and crystallization communications, 2006Co-Authors: James F. Parsons, Kelly Calabrese, Jane E. LadnerAbstract:Bacteria have evolved elaborate schemes that help them thrive in environments where free iron is severely limited. Siderophores such as yersiniabactin are small iron-scavenging molecules that are deployed by bacteria during iron starvation. Several studies have linked siderophore production and virulence. Yersiniabactin, produced by several Enterobacteriaceae, is derived from the key metabolic intermediate Chorismic Acid via its conversion to salicylate by salicylate synthase. Crystals of salicylate synthase from the uropathogen Escherichia coli CFT073 have been grown by vapour diffusion using polyethylene glycol as the precipitant. The monoclinic (P2(1)) crystals diffract to 2.5 A. The unit-cell parameters are a = 57.27, b = 164.07, c = 59.04 A, beta = 108.8 degrees. The solvent content of the crystals is 54% and there are two molecules of the 434-amino-Acid protein in the asymmetric unit. It is anticipated that the structure will reveal key details about the reaction mechanism and the evolution of salicylate synthase.
James F. Parsons - One of the best experts on this subject based on the ideXlab platform.
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Structure of Aminodeoxychorismate Synthase from Stenotrophomonas maltophilia.
Biochemistry, 2012Co-Authors: Asim K. Bera, Vesna Atanasova, Anjali Dhanda, J.e. Ladner, James F. ParsonsAbstract:PabB, aminodeoxychorismate synthase, is the Chorismic Acid binding component of the heterodimeric PabA–PabB complex that converts Chorismic Acid to 4-amino-4-deoxychorismate, a precursor of p-aminobenzoate and folic Acid in microorganisms. The second component, a glutamine amidotransferase subunit, PabA, generates ammonia that is channeled to the PabB active site where it attacks C4 of a chorismate-derived intermediate that is covalently bound, through C2, to an active site lysine residue. The presence of a PIKGT motif was, until recently, believed to allow discrimination of PabB enzymes from the closely related enzyme anthranilate synthase, which typically contains a PIAGT active site motif and does not form a covalent enzyme–substrate intermediate with chorismate. A subclass of PabB enzymes that employ an alternative mechanism requiring 2 equiv of ammonia from glutamine and that feature a noncovalently bound 2-amino-2-deoxyisochorismate intermediate was recently identified. Here we report the 2.25 A cry...
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Structure of isochorismate synthase in complex with magnesium
Acta Crystallographica Section D-biological Crystallography, 2008Co-Authors: James F. Parsons, Jane E. LadnerAbstract:The electron carrier menaquinone is one of many important bacterial metabolites that are derived from the key intermediate Chorismic Acid. MenF, the first enzyme in the menaquinone pathway, catalyzes the isomerization of chorismate to isochorismate. Here, an improved structure of MenF in a new crystal form is presented. The structure, solved at 2.0 A resolution in complex with magnesium, reveals a well defined closed active site. Existing evidence suggests that the mechanism of the reaction catalyzed by MenF involves nucleophilic attack of a water molecule on the chorismate ring. The structure reveals a well defined water molecule located in an appropriate position for activation by Lys190 and attack on the substrate.
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Crystal Structure of the Pyocyanin Biosynthetic Protein PhzS.
Biochemistry, 2008Co-Authors: Bryan T. Greenhagen, Asim K. Bera, Jane E. Ladner, Howard Robinson, Swarna A. Gamage, James F. ParsonsAbstract:The human pathogen Pseudomonas aeruginosa produces pyocyanin, a blue-pigmented phenazine derivative, which is known to play a role in virulence. Pyocyanin is produced from Chorismic Acid via the phenazine pathway, nine proteins encoded by a gene cluster. Phenazine-1-carboxylic Acid, the initial phenazine formed, is converted to pyocyanin in two steps that are catalyzed by the enzymes PhzM and PhzS. PhzM is an adenosylmethionine dependent methyltransferase, and PhzS is a flavin dependent hydroxylase. It has been shown that PhzM is only active in the physical presence of PhzS, suggesting that a protein−protein interaction is involved in pyocyanin formation. Such a complex would prevent the release of 5-methyl-phenazine-1-carboxylate, the putative intermediate, and an apparently unstable compound. Here, we describe the three-dimensional structure of PhzS, solved by single anomalous dispersion, at a resolution of 2.4 A. The structure reveals that PhzS is a member of the family of aromatic hydroxylases charact...
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Structural and functional analysis of the pyocyanin biosynthetic protein PhzM from Pseudomonas aeruginosa.
Biochemistry, 2007Co-Authors: James F. Parsons, Kelly Calabrese, Bryan T. Greenhagen, Howard Robinson, Jane E. LadnerAbstract:Pyocyanin is a biologically active phenazine produced by the human pathogen Pseudomonas aeruginosa. It is thought to endow P. aeruginosa with a competitive growth advantage in colonized tissue and is also thought to be a virulence factor in diseases such as cystic fibrosis and AIDS where patients are commonly infected by pathogenic Pseudomonads due to their immunocompromised state. Pyocyanin is also a chemically interesting compound due to its unusual oxidation−reduction activity. Phenazine-1-carboxylic Acid, the precursor to the bioactive phenazines, is synthesized from Chorismic Acid by enzymes encoded in a seven-gene cistron in P. aeruginosa and in other Pseudomonads. Phenzine-1-carboxylic Acid is believed to be converted to pyocyanin by the sequential actions of the putative S-adenosylmethionine-dependent N-methyltransferase PhzM and the putative flavin-dependent hydroxylase PhzS. Here we report the 1.8 A crystal structure of PhzM determined by single anomalous dispersion. Unlike many methyltransferas...
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Crystallization and X-ray diffraction analysis of salicylate synthase, a chorismate-utilizing enyme involved in siderophore biosynthesis.
Acta Crystallographica Section F-structural Biology and Crystallization Communications, 2006Co-Authors: James F. Parsons, Kelly Calabrese, Jane E. LadnerAbstract:Bacteria have evolved elaborate schemes that help them thrive in environments where free iron is severely limited. Siderophores such as yersiniabactin are small iron-scavenging molecules that are deployed by bacteria during iron starvation. Several studies have linked siderophore production and virulence. Yersiniabactin, produced by several Enterobacteriaceae, is derived from the key metabolic intermediate Chorismic Acid via its conversion to salicylate by salicylate synthase. Crystals of salicylate synthase from the uropathogen Escherichia coli CFT073 have been grown by vapour diffusion using polyethylene glycol as the precipitant. The monoclinic (P21) crystals diffract to 2.5 A. The unit-cell parameters are a = 57.27, b = 164.07, c = 59.04 A, β = 108.8°. The solvent content of the crystals is 54% and there are two molecules of the 434-amino-Acid protein in the asymmetric unit. It is anticipated that the structure will reveal key details about the reaction mechanism and the evolution of salicylate synthase.
Gary H Posner - One of the best experts on this subject based on the ideXlab platform.
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stereocontrolled synthesis of highly functionalized cyclohexenes a short synthesis of a Chorismic Acid precursor
ChemInform, 1990Co-Authors: Gary H Posner, Todd D NelsonAbstract:The bicyclic adducts (VII), which represent rigid, highly oxygenated cyclohexenes are useful building units for the preparation of highly functionalized cyclohexenes such as (IX), (X) and (XII).
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stereocontrolled synthesis of highly functionalized cyclohexenes a short synthesis of a Chorismic Acid precursor
Tetrahedron, 1990Co-Authors: Gary H Posner, Todd D NelsonAbstract:Abstract A convenient and mild thermal procedure has been developed for stereoselective 2+4-cycloadditions of electron-rich 1,2-dioxygenated olefins 7 to electron-deficient 3-sulfonyl-2-pyrone 6 allowing isolation of the structurally and stereochemically rich initial bicyclic adducts 8. These bicyclic adducts are shown to be useful building units as exemplified by a very short and high-yield preparation of a Chorismic Acid precursor.
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New synthetic methodology using organosulfur compounds
Pure and Applied Chemistry, 1990Co-Authors: Gary H PosnerAbstract:Electron-deficient 3-sulfur-substituted 2-pyrones are shown to cycloadd with high stereoselectivity to electron-rich vinylic ethers, vinylic thioethers, and 1,3-dioxoles under sufficiently mild conditions to allow isolation of the initial, bridged, bicyclic lactone adducts. These structurally and stereochemically rich bicycloadducts are easily converted into highly functionalized cyclohexenes as exemplified by high yield syntheses of Chorismic Acid, 4-epi-shikimic Acid, and also la, 25- dihydroxyvitamin D3.