Properties of the cytoplasmic glutamyl-tRNA synthetase in high molecular weight complexes from bovine brain.

The glutamyl-tRNA synthetase purified 300-fold from calf brain is associated with other aminoacyl-tRNA synthetases in a complex whose molecular weight is about 2,000,000. However, in a less purified state, the enzyme is present in a complex larger than 5,000,000. The properties of the enzyme are the same in both complexes except for the pH optimum of the aminoacylation reaction. The presence of 2-mercaptoethanol protects and increases the enzymatic activity. gamma-Methyl-L-glutamate and salicylate show competitive inhibition with respect to glutamate but kainic acid and taurine have no effect on the rate of aminoacylation of tRNAGlu.