Catalytical mechanism of the phenylalanyl-tRNA synthetase from yeast. Reactivity of ATP in the absence of phenylalanine

Abstract

Phenylalanyl-tRNA synthetase catalyses an AMP-ATP exchange under conditions where no aminoacylation of tRNA occurs. A plausible explanation for this reaction had not been given so far. The results of the present investigation provide evidence for the following interpretation. tRNAPhe induces a polarisation of the ATP in complex with the enzyme; this stimulates (a) the formation of phenylalanyl-adenylate in the presence of phenylalanine, (b) the hydrolysis of ATP in the absence of phenylalanine and AMP and (c) the transfer of diphosphoryl onto AMP in the presence of AMP, especially when phenylalanine is absent.