This Staphylococcus aureus enzyme catalyses the successive transfer of two glycine moieties from charged tRNAs to MurNAc-L-Ala-D-isoglutaminyl-L-Lys-(N6-tri-Gly)-D-Ala-D-Ala-diphospho-ditrans,octacis-undecaprenyl-GlcNAc, attaching them to the three glycine molecules that were previously attached to the N6 of the L-lysine at position 3 of the pentapeptide by EC 2.3.2.16 (FemX) and EC 2.3.2.17 (FemA). This is the last step in the synthesis of the pentaglycine interpeptide bridge that is used in this organism for the crosslinking of different glycan strands to each other.