22642-82-6Relevant articles and documents
The origin of the C-2 hydroxyl in the isochorismate synthase reaction
Gould,Eisenberg
, p. 5979 - 5990 (1991)
Isochorismate synthase has been isolated from Enterobacter aerogenes 62-1 and partially purified through DEAE cellulose chromatography and ammonium sulfate precipitation. When chorismic acid, 8, was treated with this preparation in 50% H21
A Thiamine-Dependent Enzyme Utilizes an Active Tetrahedral Intermediate in Vitamin K Biosynthesis
Song, Haigang,Dong, Chen,Qin, Mingming,Chen, Yaozong,Sun, Yueru,Liu, Jingjing,Chan, Wan,Guo, Zhihong
supporting information, p. 7244 - 7247 (2016/07/06)
Enamine is a well-known reactive intermediate mediating essential thiamine-dependent catalysis in central metabolic pathways. However, this intermediate is not found in the thiamine-dependent catalysis of the vitamin K biosynthetic enzyme MenD. Instead, an active tetrahedral post-decarboxylation intermediate is stably formed in the enzyme and was structurally determined at 1.34 ? resolution in crystal. This intermediate takes a unique conformation that allows only one proton between its tetrahedral reaction center and the exo-ring nitrogen atom of the aminopyrimidine moiety in the cofactor with a short distance of 3.0 ?. It is readily convertible to the final product of the enzymic reaction with a solvent-exchangeable proton at its reaction center. These results show that the thiamine-dependent enzyme utilizes a tetrahedral intermediate in a mechanism distinct from the enamine catalytic chemistry.
Genetic and biochemical analyses of chromosome and plasmid gene homologues encoding ICL and ArCP domains in Vibrio anguillarum strain 775
Di Lorenzo, Manuela,Stork, Michiel,Crosa, Jorge H.
experimental part, p. 629 - 643 (2012/04/11)
Anguibactin, the siderophore produced by Vibrio anguillarum 775 is synthesized from 2,3-dihydroxybenzoic acid (DHBA), cysteine and hydroxyhistamine via a nonribosomal peptide synthetase (NRPS) mechanism. Most of the genes encoding anguibactin biosynthetic proteins are harbored by the pJM1 plasmid. In this work we report the identification of a homologue of the plasmid-encoded angB on the chromosome of strain 775. The product of both genes harbor an isochorismate lyase (ICL) domain that converts isochorismic acid to 2,3-dihydro-2,3-dihydroxybenzoic acid, one of the steps of DHBA synthesis. We show in this work that both ICL domains are functional in the production of DHBA in V. anguillarum as well as in E. coli. Substitution by alanine of the aspartic acid residue in the active site of both ICL domains completely abolishes their isochorismate lyase activity in vivo. The two proteins also carry an aryl carrier protein (ArCP) domain. In contrast with the ICL domains only the plasmid encoded ArCP can participate in anguibactin production as determined by complementation analyses and site-directed mutagenesis in the active site of the plasmid encoded protein, S248A. The site-directed mutants, D37A in the ICL domain and S248A in the ArCP domain of the plasmid encoded AngB were also tested in vitro and clearly show the importance of each residue for the domain function and that each domain operates independently.
Crystal Structure of Escherichia coli Enterobactin-specific Isochorismate Synthase (EntC) Bound to its Reaction Product Isochorismate: Implications for the Enzyme Mechanism and Differential Activity of Chorismate-utilizing Enzymes
Sridharan, Sudharsan,Howard, Nigel,Kerbarh, Olivier,Blaszczyk, Michal,Abell, Chris,Blundell, Tom L.
experimental part, p. 290 - 300 (2011/05/16)
EntC, one of two isochorismate synthases in Escherichia coli, is specific to the biosynthesis of the siderophore enterobactin. Here, we report the crystal structure of EntC in complex with isochorismate and Mg2+at 2.3 A resolution, the first structure of a chorismate-utilizing enzyme with a non-aromatic reaction product. EntC exhibits a complex α+β fold like the other chorismate-utilizing enzymes, such as salicylate synthase and anthranilate synthase. Comparison of active site structures allowed the identification of several residues, not discussed previously, that might be important for the isochorismate activity of the EntC. Although EntC, MenF and Irp9 all convert chorismate to isochorismate, only Irp9 subsequently exhibits isochorismate pyruvate lyase activity resulting in the formation of salicylate and pyruvate as the reaction products. With a view to understanding the roles of these amino acid residues in the conversion of chorismate to isochorismate and to obtaining clues about the pyruvate lyase activity of Irp9, several mutants of EntC were generated in which the selected residues in EntC were substituted for those of Irp9: these included A303T, L304A, F327Y, I346L and F359Q mutations. Biochemical analysis of these mutants indicated that the side chain of A303 in EntC may be crucial in the orientation of the carbonyl to allow formation of a hydrogen bond with isochorismate. Some mutations, such as L304A and F359Q, give rise to a loss of catalytic activity, whereas others, such as F327Y and I346L, show that subtle changes in the otherwise closely similar active sites influence activity. We did not find a combination of these residues that conferred pyruvate lyase activity.
Effects of macromolecular crowding on the intrinsic catalytic efficiency and structure of enterobactin-specific isochorismate synthase
Jiang, Ming,Guo, Zhihong
, p. 730 - 731 (2007/10/03)
Macromolecular crowding was found to significantly enhance the intrinsic catalytic efficiency of the enterobactin-specific isochorismate synthase by inducing structural change in the enzyme. This finding provides the first experimental evidence that macro
Experimental and computational investigation of the uncatalyzed rearrangement and elimination reactions of isochorismate
DeClue, Michael S.,Baldridge, Kim K.,Kast, Peter,Hilvert, Donald
, p. 2043 - 2051 (2007/10/03)
The versatile biosynthetic intermediate isochorismate decomposes in aqueous buffer by two competitive pathways, one leading to isoprephenate by a facile Claisen rearrangement and the other to salicylate via elimination of the enolpyruvyl side chain. Computation suggests that both processes are concerted but asynchronous pericyclic reactions, with considerable C-O cleavage in the transition state but relatively little C-C bond formation (rearrangement) or hydrogen atom transfer to the enolpyruvyl side chain (elimination). Kinetic experiments show that rearrangement is roughly 8-times more favorable than elimination. Moreover, transfer of the C2 hydrogen atom to C9 was verified by monitoring the decomposition of [2-2H]isochorismate, which was prepared chemoenzymatically from labeled shikimate, by 2H NMR spectroscopy and observing the appearance of [3-2H]pyruvate. Finally, the isotope effects obtained with the C2 deuterated substrate are in good agreement with calculations assuming pericyclic reaction mechanisms. These results provide a benchmark for mechanistic investigations of isochorismate mutase and isochorismate pyruvate lyase, the enzymes that respectively catalyze the rearrangement and elimination reactions in plants and bacteria.
