Binding pattern of intermediate UDP-4-keto-xylose to human UDP-xylose synthase: Synthesis and STD NMR of model keto-saccharides

作者：Puchner Claudia; Eixel**erger Thomas; Nidetzky Bernd; Brecker Lothar^*

来源：Carbohydrate Research, 2017, 437: 50-58.

DOI：10.1016/j.carres.2016.11.001

• 4-Keto-saccharides
• Human UDP-xylose synthase
• Saturation transfer difference NMR
• Binding pattern

Human UDP-xylose synthase (hUXS1) exclusively converts UDP-glucuronic acid to UDP-xylose via intermediate UDP-4-keto-xylose (UDP-Xyl-4O). Synthesis of model compounds like methyl-4-keto-xylose (Me-Xyl-4O) is reported to investigate the binding pattern thereof to hUXS1. Hence, selective oxidation of the desired hydroxyl function required employment of protecting group chemistry. Solution behavior of synthesized keto-saccharides was studied without enzyme via H-1 and C-13 NMR spectroscopy with respect to existent forms in deuterated potassium phosphate buffer. Keto-enol tautomerism was observed for all investigated keto-saccharides, while gem-diol hydrate forms were only observed for 4keto-xylose derivatives. Saturation transfer difference (STD) NMR was used to study binding of synthesized keto-gylcosides to wild type hUXS1. Resulting epitope maps were correlated to earlier published molecular modeling studies of UDP-Xyl-4O. STD NMR results of Me-Xyl-4O are in good agreement with simulations of the intermediate UDP-Xy1-4O indicating a strong interaction of proton H3 with the enzyme, potentially caused by active site residue Ala(79). In contrast, pyranoside binding pattern studies of methyl uronic acids showed some differences compared to previously published STD NMR results of UDP-glycosides. In general, obtained results can contribute to a better understanding in binding of UDPglycosides to other UXS enzyme family members, which have high structural similarities in the active site.

• 出版日期2017-1-2