N-acetylglucosamine kinase (NAGK)

Abstract

N-Acetylglucosamine kinase (GlcNAc kinase; NAGK) catalyzes the phosphorylation of GlcNAc at C-6 by the use of ATP (Fig. 131.1). Cellular GlcNAc is usually provided by a de novo pathway starting from glycolysis at fructose 6-phosphate. Reutilization of GlcNAc from nutritional sources or lysosomal degradation of oligosaccharides is performed in a salvage pathway, which is initiated by GlcNAc kinase and the formation of GlcNAc 6-phosphate (Fig. 131.1). GlcNAc 6-phosphate then enters an anabolic pathway leading to the formation of UDP-GlcNAc, which is the substrate for the large set of GlcNAc transferases in complex oligosaccharide synthesis and the intracellular O-GlcNAc formation, or it is further metabolized to N-acetylneuraminic acid within the sialic acid biosynthesis (Fig. 131.1). GlcNAc 6-phosphate may also enter a catabolic pathway, which links hexosamine metabolism with the glycolytic pathway and the formation of fructose 6-phosphate.