Involved in the pathway of N-acetyl-D-galactosamine degradation. Catalyzes the phosphorylation of N-acetyl-D-galactosamine (GalNAc) to yield D-galactosamine 6-phosphate (GalN-6-P). It can also phosphorylate N-acetylglucosamine (GlcNAc). ATP + N-acetyl-D-galactosamine = ADP + H(+) + N-acetyl-D-galactosamine 6-phosphate ATP + N-acetyl-D-glucosamine = ADP + H(+) + N-acetyl-D-glucosamine 6-phosphate kcat is 40.3 sec(-1) for kinase activity with GalNAc as substrate. kcat is 7.1 sec(-1) for kinase activity with GlcNAc as substrate. In Shewanella sp., the active phosphotransferase system (PTS) specific for the transport of GalNAc and GalN is replaced by a set of GalNAc- and GalN-specific permeases and kinases (AgaP and AgaK, respectively). Belongs to the ROK (NagC/XylR) family.