Catalyzes the incorporation of amino acid(s) into the interchain peptide bridge of peptidoglycan, using aminoacyl-tRNA as amino acid donor. 2 glycyl-tRNA(Gly) + MurNAc-L-Ala-D-isoglutaminyl-L-Lys-(N(6)-tri-Gly)-D-Ala-D-Ala-diphospho-di-trans,octa-cis-undecaprenyl-GlcNAc = 2 H(+) + MurNAc-L-Ala-D-isoglutaminyl-L-Lys-(N(6)-penta-Gly)-D-Ala-D-Ala-diphospho-di-trans,octa-cis-undecaprenyl-GlcNAc + 2 tRNA(Gly) Belongs to the FemABX family.