A novel enzymatic activity of phenylalanyl transfer ribonucleic acid synthetase from baker's yeast: zinc ion induced transfer ribonucleic acid independent hydrolysis of adenosine triphosphate.

Phenylalanyl-tRNA synthetase from baker's yeast in the presence of phenylalanine or other amino acids misactivated by the enzyme, ATP, and low concentrations of Zn2+ is able to hydrolyze ATP to AMP and PPi very efficiently. After dialysis of the enzyme against ethylenediaminetetraacetic acid (EDTA), this amino acid dependent but tRNAPhe-independent hydrolysis is suppressed to negligible levels. The ATP hydrolysis can be restored by the addition of Zn2+ to the EDTA-dialyzed enzyme. During aminoacylation of tRNAPhe the Zn2+-induced ATP hydrolysis parallels the aminoacylation reaction, leading to nonstoichiometric production of AMP. Mechanistically, we conclude that Zn2+ can be bound to phenylalanyl-tRNA synthetase and can influence the stability of ATP if an activatable amino acid is present. The influence of Zn2+, if any, on the aminoacylation of tRNAPhe is not known. In practice, this side reaction is of the utmost importance in all cases in which the fate of ATP during aminoacylation is followed, especially if the stoichiometry of ATP consumption in relation to Phe-tRNAPhe formation has to be determined.