ENZYME-ENZYME INTERACTION AND THE BIOSYNTHESIS OF AROMATIC AMINO-ACIDS IN ESCHERICHIA-COLI

The technique of affinity chromatography has been used to demonstrate that enzymes involved in the biosynthesis of tyrosine and phenylalanine in Escherichia coli undergo reversible interactions. Thus it has been shown that the aromatic amino acid aminotransferase (aromatic-amino-acid: 2-oxoglutarate amino-transferase, EC 2.6.1.57) reacts specifically with chorismate mutase-prephenate dehydrogenase (chorismate pyruvate mutase, EC 5.4.99.5 and prephenate: NAD+ oxidoreductase (decarboxylating), EC 1.3.1.12) in the absence of reactants and with chorismate mutase-prephenatedehydratase (prephenate hydro-lyase (decarboxylating), EC 4.2.1.51) in the presence of phyenylpyruvate. Tyrosine causes dissociation of the aminotransferase: mutase-dehydrogenase complex while dissociation of the aminotransferase-mutase-dehydratase complex occurs on omission of phenylpyruvate. Only the active form of chorismate mutase-prephenate dehydrogenase participates in complex formation. © 1979.