D-Glucosamine is made naturally in the form of glucosamine-6-phosphate, and is the biochemical precursor of all nitrogen-containing sugars.

[1] To be specific, glucosamine-6-phosphate is synthesized from fructose 6-phosphate and glutamine[2] as the first step of the hexosamine biosynthesis pathway.

[4] UDP-GlcNAc is extensively involved in intracellular signaling as a substrate for O-linked N-acetylglucosamine transferases (OGTs) to install the O-GlcNAc post-translational modification in a wide range of species.

In mammals, there is enrichment of OGT transcripts in the pancreas beta-cells, and UDP-GlcNAc is thought to be part of the glucose sensing mechanism.

[5] Clostridium novyi type A alpha-toxin is an O-linked N-actetylglucosamine transferase acting on Rho proteins and causing the collapse of the cytoskeleton.