Catalyzes the phosphorylation of N-acetyl-D-glucosamine (GlcNAc) derived from cell-wall degradation, yielding GlcNAc-6-P. ATP + N-acetyl-D-glucosamine = ADP + H(+) + N-acetyl-D-glucosamine 6-phosphate Cell wall biogenesis; peptidoglycan recycling. Might be inactive, since the sequence is shorter than in other family members, due to a probable natural frameshift in the C-terminus. Belongs to the ROK (NagC/XylR) family. NagK subfamily.