Figure 1.

The hexosamine biosynthetic pathway (HBP) and the GlcNAc salvage pathway yield UDP‐GlcNAc (2). Glutamine fructose amidotransferase (GFAT) catalyzes the conversion of glucosamine (5) into glucosamine‐6‐phosphate (GlcNH₂‐6PO₄; 5‐6PO₄). Acetylation of 5‐6PO₄ by glucosamine acetyltransferase (GAT) yields GlcNAc‐6PO₄, an intermediate also produced by GlcNAc kinase (GNK) in the GlcNAc salvage pathway. The sequential action of phosphoglucosamine mutase (AGM) and GlcNAc pyrophosphorylase (AGX) on GlcNAc‐6PO₄ leads to the formation of UDP‐GlcNAc (2). 5SGlcNAc (3) can be similarly salvaged and converted into UDP‐5SGlcNAc (4).