In the first set of
reactions, glucose-6-phosphate is converted to glucose-
1-phosphate by a-phosphoglucomutase. UDP-glucose
pyrophosphorylase adds UTP to glucose-1-phosphate to
produce UDP-glucose. Finally, oxidation of the primary
alcohol in UDP-glucose by UDP-glucose dehydrogenase
yields the first HA precursor, UDP-glucuronic acid.