title: The purification and molecular properties of the tryptophan-sensitive 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase from Neurospora crassa.
abstract: Neurospora crassa contains three isoenzymes of 3-deoxy-D-arabino-heptulosonate 7-phosphate synthase, which are inhibited by tyrosine, tryptophan and phenylalanine respectively, and it was estimated that the relative proportions of the total activity were 54%, 14% and 32% respectively. The tryptophan-sensitive isoenzyme was purified to homogeneity as judged by polyacrylamide-gel electrophoresis and ultracentrifugation. The tyrosine-sensitive and phenylalanine-sensitive isoenzymes were only partially purified. The three isoenzymes were completely separated from each other, however, and can be distinguished by (NH4)2SO4 fractionation, chromatography on DEAE-cellulose and Ultrogel AcA-34 and polyacrylamide-gel electrophoresis. Polyacrylamide-gel electrophoresis in the presence of sodium dodecyl sulphate indicated that the tryptophan-sensitive isoenzyme contained one type of subunit of molecular weight 52000. The molecular weight of the native enzyme was found to be 200000 by sedimentation-equilibrium centrifugation, indicating that the enzyme is a tetramer, and the results of cross-linking and gel-filtration studies were in agreement with this conclusion.
mesh_terms: D010723:3-Deoxy-7-Phosphoheptulonate Synthase / Q000037:antagonists & inhibitors / Q000302:isolation & purification; D000446:Aldehyde-Lyases / Q000302:isolation & purification; D002848:Chromatography, DEAE-Cellulose; D002850:Chromatography, Gel; D002852:Chromatography, Ion Exchange; D004591:Electrophoresis, Polyacrylamide Gel; D007527:Isoenzymes / Q000037:antagonists & inhibitors / Q000302:isolation & purification; D009491:Neurospora / Q000201:enzymology*; D009492:Neurospora crassa / Q000201:enzymology*; D014364:Tryptophan / Q000494:pharmacology; D014461:Ultracentrifugation
chemical_list: D007527:Isoenzymes; D014364:Tryptophan; D010723:3-Deoxy-7-Phosphoheptulonate Synthase; D000446:Aldehyde-Lyases