title: Purification and properties of DAHP synthase from Nocardia mediterranei.
abstract: 3-Deoxy-D-arabino-heptulosonate-7-phosphate (DAHP) synthase, the first enzyme of the shikimate pathway was isolated from Nocardia mediterranei. It has a molecular weight of approx. 135,000, and four identical subunits, each with a molecular weight of 35,000. The Km values for phosphoenolpyruvate (PEP) and D-erythrose 4-phosphate (E-4-P) were 0.4 and 0.25 mM, respectively, and kinetic study showed that LTrp inhibited DAHP synthase activity, but was not competitive with respect to PEP or E-4-P. The enzyme activity was inhibited by excess of E-4-P added in the incubation system. D-ribose 5-phosphate (R-5-P), D-glucose 6-phosphate (G-6-P) or D-sedoheptulose 7-phosphate (Su-7-P) etc. inhibited DAHP synthase in cell-free extract, but on partially purified enzyme no inhibitory effect was detected. The indirect inhibition of R-5-P and other sugar phosphates was considered to be due to the formation of E-4-P catalyzed by the related enzymes present in cell-free extract.
authors.affiliation: Shanghai Institute of Plant Physiology, Academia Sinica Shanghai (Peoples Republic of China).
authors.forename: T H
authors.initials: TH
authors.lastname: Xia
authors.forename: J S
authors.initials: JS
authors.lastname: Chiao
mesh_terms: D010723:3-Deoxy-7-Phosphoheptulonate Synthase / Q000302:isolation & purification* / Q000378:metabolism; D000446:Aldehyde-Lyases / Q000302:isolation & purification*; D002384:Catalysis; D002474:Cell-Free System; D002850:Chromatography, Gel; D004591:Electrophoresis, Polyacrylamide Gel; D006863:Hydrogen-Ion Concentration; D009615:Nocardia / Q000201:enzymology*; D013403:Sugar Phosphates / Q000494:pharmacology
chemical_list: D013403:Sugar Phosphates; D010723:3-Deoxy-7-Phosphoheptulonate Synthase; D000446:Aldehyde-Lyases