When this enzyme acts on tRNAGlu, it catalyses the same reaction as EC 184.108.40.206, glutamate---tRNA ligase. It has, however, diminished discrimination, so that it can also form glutamyl-tRNAGln. This relaxation of specificity has been found to result from the absence of a loop in the tRNA that specifically recognizes the third position of the anticodon . This accounts for the ability of this enzyme in, for example, Bacillus subtilis, to recognize both tRNA1Gln (UUG anticodon) and tRNAGlu (UUC anticodon) but not tRNA2Gln (CUG anticodon). The ability of this enzyme to recognize both tRNAGlu and one of the tRNAGln isoacceptors derives from their sharing a major identity element, a hypermodified derivative of U34 (5-methylaminomethyl-2-thiouridine). The glutamyl-tRNAGln is not used in protein synthesis until it is converted by EC 220.127.116.11, glutaminyl-tRNA synthase (glutamine-hydrolysing), into glutaminyl-tRNAGln.