Engineering the Stability of Sucrose Synthase to Enable Efficient Coupled Production of UDP-Glucuronic Acid.

The biocatalytic synthesis of UDP-glucuronic acid (UDPGA), a key precursor for glucuronides and high-value carbohydrates, is limited by an unstable UDP-glucose (UDPG) supply in coupled systems. In this study, through an extensive screening of 10 sucrose synthases derived from both eukaryotic and prokaryotic microorganisms, we identified a broad-spectrum, highly efficient enzymatic scaffold suitable for the synthesis of UDP-sugars. A rational design integrating PROSS and ThermoMPNN algorithms with molecular dynamics (MD) analysis yielded the V353L mutant, which retained 97% of wild-type activity and extended the half-life at 55°C from 0.4 to 5.5 h. Tetrameric MD simulations indicated that V353L strengthens hydrophobic stacking in the GT-B linker region, reducing conformational fluctuations and driving the enzyme toward a stable low-energy state. In a dual-enzyme cascade synthesizing UDPG and UDPGA, the mutant sustained UDP consumption and increased the accumulated UDPGA concentration from 0.60 to 2.09 mM after 8 h. Engineering sucrose synthase thermostability thus improves UDPG supply in cascade biocatalysis and offers a viable enzymatic strategy for UDPGA-centered synthesis of high-value carbohydrate derivatives.