ATP-analogues as substrates for the leucyl-tRNA synthetase from Escherichia coli MRE 600.

No analogous nucleoside triphosphate was found which acts as well as ATP in binding to and supporting catalysis of leucyl-tRNA synthetase from Escherichia coli MRE 600. However, there are numerous nucleotides which are able to replace ATP, but with lower efficiency. The 6-amino group of the adenine ring and the 2'-hydroxyl group of the ribose ring are essential for binding and catalytic activity. Alterations in the triphosphate moiety of the molecule can cause drastic changes in Km and/or Vmax, whereas alterations of the imidazole ring and substitutions at the 8-position of the adenine ring cause only minor losses of catalytic activity.