GlcNAc-1-P in the presence of UTP is converted to UDP-GlcNAc and PPi anabolically (the catabolic reaction is the reverse) by UDP-N-acetylglucosamine pyrophosphorylase, and UDP-GlcNAc is epimerized to UDP-GalNAc by UDP-N-acetylglucosamine 4′-epimerase (10). The UDP-GlcNAc produced in this ...