Showing papers by "Earl W. Davie published in 1962"

[97] Tryptophan-activating enzyme: ATP + TRY + NH2OH → AMP + PP + TRY-NHOH

Abstract: Publisher Summary This chapter describes the assay methods, purification procedure, and properties of tryptophan-activating enzyme. The mechanism of the reaction for the activation of tryptophan involves a pyrophosphoryl split of ATP with the intermediate formation of an enzyme-bound amino acyl adenylate. In the presence of an RNA aceeptor, an amino acid-RNA compound plus free AMP are formed. The assay methods for this enzyme in the absence of RNA acceptor usually involve the amino acid-dependent PP, incorporation into ATP or the formation of the amino acid hydroxamic acid in the presence of hydroxylamine. Only the method using hydroxylamine is described in the chapter. The purified preparations are stable indefinitely when frozen as ammonium sulfate precipitates. The enzyme is specific for the L-amino acid possessing a free amino group. Several analogs replaceS tryptophan. These include tryptozan, azatryptophan, and 5-fluorotryptophan. The enzyme is specific for ATP. In the reverse reaction, the enzyme shows little specificity for the formation of ATP from adenyl amino acids and pyrophosphate.