Practical Enzyme-Based Syntheses of Uridine 5'-Diphosphogalactose and Uridine 5'-Diphospho-/V-acetylgalactosamine on a Gram Scaler

Practical enzyme-based routes for the syntheses of uridine 5'-diphosphogalactose (UDP-Gal) and uridine 5'-diphospho-N-acetylgalactosamine (UDP-GalNAc) on millimole scales have been developed. The activity of galactokinase (EC 2.7.L.6) in crude enzyme extracts from galactose-adapted yeast, coupled to a regenerating system for ATP, provides convenient and economical access to galactose-a-1-phosphate (Gal-1-P) and galactosaminea-l-phosphate (GalN-l-P). The transfer of UMP to the sugar-l-phosphates was also accomplished enzymatically bv Gal-1-P uridyltransferase (EC 2.7.7.12) using uridine 5'-diphosphoglucose (UDP-Glc) as the UMP donor. UDP-Glc was in turn regenerated in situ from glucose-l-phosphate and UTP using UDP-Glc pyrophosphorylase (EC 2.7.7.il. The only chemical step in the sequence was the acetylation of UDP-GaIN to afford UDP-GalNAc using N-acetoxysuccinimide. The moderate overall yields (a3% and34Vo for UDP-Gal and UDP-GalNAc from Gal-l-P and Galll-l-P, respectively) were compensated by the straightforward preparation of the starting materials, UTP and the corresponding sugar-1-P.