Creating Space for Large Acceptors: Rational Biocatalyst Design for Resveratrol Glycosylation in an Aqueous System

Polyphenols display a number of interesting properties but their low solubility limits practical applications. In that respect, glycosylation offers a solution for which sucrose phosphorylase has been proposed as a cost‐effective biocatalyst. However, its activity on alternative acceptor substrates is too low for synthetic purposes and typically requires the addition of organic (co‐)solvents. Here, we describe the engineering of the enzyme from Thermoanaerobacterium thermosaccharolyticum to enable glycosylation of resveratrol as test case. Based on docking and modeling studies, an active‐site loop was predicted to hinder binding. Indeed, the unbolted loop variant R134A showed useful affinity for resveratrol (Km=185 mM) and could be used for the quantitative production of resveratrol 3‐α‐glucoside in an aqueous system. Improved activity was also shown for other acceptors, introducing variant R134A as promising new biocatalyst for glycosylation reactions on bulky phenolic acceptors. Biocatalyst design: Based on modeling and docking studies, a thermostable sucrose phosphorylase was engineered to enable access of large acceptor substrates. The site‐specific loop variant R134A showed high transglycosylation activity on resveratrol in an aqueous system, requiring only sucrose as a cheap glycosyl donor. Significant promiscuity towards a range of other polyphenolic acceptors is also reported.