3-Deoxy-D-arabino-heptulosonate 7-phosphate synthase. Purification, properties, and kinetics of the tyrosine-sensitive isoenzyme from Escherichia coli.

Crystal structure of phenylalanine-regulated 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase from Escherichia coli

“…The less abundant isozymes, DAHPS(Trp) (1% of total activity) and DAHPS(Tyr) (20% of total activity) are homodimers encoded by the aroH and aroF genes, respectively. Consistent with their multimeric structures, the DAHPS isozymes of E. coli exhibit positive, homotropic cooperativity in the kinetics of E4P and PEP utilization and heterotropic interactions in the kinetics of feedback inhibition [4][5][6].…”

“…The clustering of the four His217 residues near the intersections of the twofold axes is especially interesting and contributes to the interaction between the two tight dimers. In addition to the stacked imidazole rings of monomers A and D In spite of the similarity in sequence between the three DAHPS isozymes, DAHPS(Tyr) and DAHPS(Trp) are dimers in solution [4,14] rather than tetramers like DAHPS(Phe) [2,16]. It is likely that the tight dimer of DAHPS(Phe) is a close structural analog of the dimeric DAHPS isoforms.…”

The purification and molecular properties of the tryptophan-sensitive 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase from Neurospora crassa

“…Assay of 3-deoxy-D-arabino-heptulosonate 7phosphate synthase activity Continuous assay method. The synthase activity was routinely assayed by the method of Schoner & Herrmann (1976). The standard assay mixture (1 ml) contained 5OmM-Bistrispropane/HCI buffer, pH 7.4, 0.4 mM-D-erythrose 4-phosphate, 0.4 mmphosphoenolpyruvate and enzyme.…”

Reciprocal allostery arising from a bienzyme assembly controls aromatic amino acid biosynthesis in Prevotella nigrescens

“…A modified continuous assay for the spectrophotometric analysis of either DAH7PS or CM enzymatic activity (37) was employed to determine the kinetic parameters of the wild-type enzyme and PniDAH7PS Δ5AA . In the standard assay, a 50 mM Bis-Tris propane (BTP) buffer (pH 7.4) was applied for either DAH7PS or CM catalysed reaction.…”

“…In the standard assay, a 50 mM Bis-Tris propane (BTP) buffer (pH 7.4) was applied for either DAH7PS or CM catalysed reaction. Enzymatic reactions were carried out in 1 ml quartz cuvettes with 1 cm path length at 35 C, and the reaction rates were monitored by the disappearance of the substrate PEP at 232 nm (2800 M −1 cm −1 ) or chorismate at 274 nm (e = 2630 M −1 cm −1 ) for the DAH7PS and CM activities, respectively (37,38). To avoid influence from unexpected metal ions, buffer and all reactions components were prepared using the ultrapure water pretreated by chelating ion exchange resin, Chelex 100 (BioRad).…”