Valyl-tRNA, isoleucyl-tRNA and tyrosyl-tRNA synthetase from baker's yeast. Substrate specificity with regard to ATP analogs and mechanism of the aminoacylation reaction.

Nineteen analogs of ATP have been tested in the aminoacylation of valyl-tRNA, isoleucyl tRNA and tyrosyl-tRNA synthetases from baker's yeast. Four compounds are substrates for valyl tRNA and two for isoleucyl-tRNA synthetase, but there is no modified substrate for the tyrosyl tRNA synthetase. There is one inhibitor for valyl-tRNA synthetase, eight compounds inhibit isoleucyl-tRNA synthetase and two compounds inhibit tyrosyl-tRNA synthetase. Their Km and Ki and V values have been determined. The substrate specificity shows that positions 2, 6, 7, 8, 9, 2', and 3' of ATP are important for catalytic action of these aminoacyl-tRNA synthetases.