title: Kinetic and regulatory properties of arogenate dehydratase in seedlings of Sorghum bicolor (L.) Moench.
abstract: Arogenate dehydratase was purified sixfold from an extract of etiolated seedlings of Sorghum bicolor. Prephenate dehydratase was not detected. The arogenate dehydratase activity displayed hyperbolic substrate kinetics with a KM for arogenate of 0.32 mM. Activity was inhibited competitively by phenylalanine and was stimulated by tyrosine. The low KI for phenylalanine (24 microM) and KA for tyrosine (2.5 microM) indicated a high affinity of the enzyme for these effectors. These results establish the routing of metabolites in phenylalanine biosynthesis in sorghum as proceeding via arogenate rather than phenylpyruvate.
mesh_terms: D000600:Amino Acids, Dicarboxylic / Q000378:metabolism; D001667:Binding, Competitive; D002848:Chromatography, DEAE-Cellulose; D053138:Cyclohexenes; D004229:Dithiothreitol / Q000494:pharmacology; D004492:Edetic Acid / Q000494:pharmacology; D004789:Enzyme Activation / Q000187:drug effects; D005978:Glutathione / Q000494:pharmacology; D006836:Hydro-Lyases / Q000037:antagonists & inhibitors / Q000302:isolation & purification / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007700:Kinetics; D010649:Phenylalanine / Q000096:biosynthesis / Q000494:pharmacology; D010944:Plants / Q000201:enzymology*; D014443:Tyrosine / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000600:Amino Acids, Dicarboxylic; D053138:Cyclohexenes; D014443:Tyrosine; D010649:Phenylalanine; C015478:pretyrosine; D004492:Edetic Acid; D006836:Hydro-Lyases; C022437:pretyrosine dehydratase; D005978:Glutathione; D004229:Dithiothreitol