432463.fig.004
Figure 4: Glucosamine biosynthesis. HK: hexokinase; Gluc-6-P: glucose-6-phosphate; Fruc-6-P: fructose-6-phosphate; GFAT: glucosamine fructose-6-phosphate amindotransferase; GlucN-6-P: Glucosamine-6-phosphate; GlucNAc-6-P: N-acetyl-glucosamine-6-phosphate; GlucNAc-1-P: N-acetyl-glucosamine-1-phosphate; UDPGalNAc: uridine diphosphate (UDP)-N-acetyl-galactosamine; UDP-GlucNAc: UDP-N-acetyl-glucosamine. Glucosamine may be obtained from exogenous supplements, or it may be endogenously synthesized from glucose through the hexosamine pathway, an alternate pathway to glycolysis. Its product is uridine 5-diphosphate-N-acetyl-glucosamine (UDP-N-Acetyl-GluN), which is a precursor for glycosaminoglycans, proteoglycans, and glycoproteins. (Refer to text.)