SYNTHESIS OF UDP-4-DEOXY-4-FLUOROGLUCOSE AND UDP-4-DEOXY-4-FLUOROGALACTOSE AND THEIR INTERACTIONS WITH ENZYMES OF NUCLEOTIDE SUGAR METABOLISM

Fluorinated carbohydrates can be used as probes of enzymatic active si tes. We report the synthesis of 4-deoxy-4-fluoro-alpha-D-galactose-1-p hosphate and the substrate analogues of UDP-galactose, UDP-4-deoxy-4-f luoro-alpha-D-galactose (UDP-FGal), and of UDP-glucose, UDP-4-deoxy-4- fluoro-alpha-D-glucose (UDP-FGlc), which may be useful in analyzing th e binding properties of enzymes that utilize nucleotide sugars as subs trates. As a first step in this study, we determine the kinetic and in hibition parameters for UDP-FGal and UDP-FGlc interacting with UDP-glu cose dehydrogenase and UDP-galactose 4-epimerase. UDP-FGlc is a substr ate for bovine liver UDP-glucose dehydrogenase: K-m = 30.2 +/- 4.5 mu M slightly higher than the value 9.6 +/- 0.7 mu M for UDP-glucose, and V-mUDP-FGlc = 046V (mUDP-Glc). UDP-FGal is not a substrate for UDP-gl ucose dehydrogenase but is a competitive inhibitor with respect to UDP -glucose (K-i = 19.9 +/- 6.6 mu M). These analogs also bind to UDP-gal actose 4-epimerase from E. coli with dissociation constants K-d of 1.4 and 1.1 mM for UDP-FGlc and UDP-FGal, respectively.