NAGK is a member of the eukaryotic-type N-acetylglucosamine kinase family. NAGK catalyzes the first committed step in arginine biosynthesis in organisms that perform the cyclic pathway of ornithine synthesis. In eukaryotic and bacterial oxygenic phototrophs, the activity of NAGK is controlled by the P(II) signal transduction protein. NAGK converts endogenous N-acetylglucosamine (GlcNAc), a key component of complex carbohydrates, from lysosomal degradation or alimentary sources into GlcNAc 6-phosphate.