Fig. 1.

Generation of the OGT substrate, UDP-GlcNAc – an overview of the hexosamine biosynthetic pathway. The hexosamine biosynthetic pathway (HBP) integrates many extracellular physiological inputs, including nutritional intake, with the metabolism of key carbohydrate, amino acid, nucleotide and fatty acid components, to produce the OGT substrate UDP-GlcNAc. O-GlcNAc cycling, the dynamic addition to and removal of O-GlcNAc on serine or threonine residues of a plethora of OGT and OGA targets, allows for the regulation of important downstream cellular processes in a nutrient-dependent manner. The enzymes involved are given in brackets.