Functional characterization of a UDP-xylose-preferring <i>C</i>-glycosyltransferase from <i>Lemna aequinoctialis</i>

Abstract

<italic>C</italic>-glycosides are an important class of bioactive natural products, and the <italic>C</italic>-glycosidic bonds are usually catalyzed by <italic>C</italic>-glycosyltransferases. In this work, an efficient and rare CGT, LaCGT1, was discovered from the aquatic plant <italic>Lemna aequinoctialis</italic>. LaCGT1 could accept five sugar donors (UDP-Glc/-Xyl/-Gal/-GlcNAc/-Ara) to catalyze <italic>C</italic>-glycosylation, and showed strong preference to uridine 5′-diphosphate xylose (UDP-Xyl). LaCGT1 catalyzed at least six substrates using UDP-Xyl as sugar donor, with conversion rates of &gt; 95%. Three xylosides were obtained by scaled-up enzymatic catalysis, and their structures were identified by 1D NMR, 2D NMR, and HR-ESIMS data analyses. Molecular modeling and site-directed mutagenesis indicated that R271, W357, D378, and Q379 residues were key amino acids contributing to sugar donor recognition of UDP-Xyl. LaCGT1 could be a promising catalyst to prepare bioactive flavonoid <italic>C</italic>-xylosides.