Synthesis of uridine 5′-monophosphate glucose as an inhibitor of UDP-glucose pyrophosphorylase

Uridine 5′-monophosphate α-d-glucose (UMPG) was evaluated as a novel and potent inhibitor of the enzymatic reaction involved in sugar nucleotide metabolism. UMPG was synthesized by chemical coupling of 2,3,4,6-tetra-O-acetyl-α-d-glucopyranosyl bromide with uridine 5′-monophosphate (UMP) to give uridine 5′-monophosphate 2″,3″,4″,6″-tetra-O-acetyl-α-d-glucose (UMPTAG), followed by deacetylation of UMPTAG with sodium methoxide. In addition to UMPG, UMPTAG showed potent inhibitory activity toward yeast UDPG pyrophosphorylase (UDPG synthetase). UMPG and UMPTAG were competitive with UDPG in the pyrophosphorolytic reaction, with inhibition constants (K_i) of 4.8 and 20.7 μM, respectively, but non-competitive with inorganic pyrophosphate. UMPG and UMPTAG also inhibited the enzyme non-competitively in the reverse reaction to synthesize UDPG from UTP and glucose 1-phosphate (G1P). The acetyl group of UMPTAG was thought to enhance its hydrophobic interaction, possibly with an active site region of the enzyme functional for binding with UDPG.