Int J Biol Macromol. 2026 Apr 20:152149. doi: 10.1016/j.ijbiomac.2026.152149. Online ahead of print.
ABSTRACT
Rheum palmatum L. is a high-value, multipurpose species widely recognized for its dual utility as both a medicinal and edible plant, possessing significant economic importance across temperate regions. Its primary bioactive constituents, anthraquinone glycosides, exhibit potent pharmacological properties, including anti-inflammatory, hepatoprotective, and antioxidant activities. However, the specific enzymatic pathways and key UDP-glycosyltransferases (UGTs) responsible for anthraquinone glycosylation in R. palmatum remain poorly understood. In this study, four novel UGTs were identified as putative candidates involved in the biosynthesis of these glycosides. These UGTs contain the conserved PSPG motif characteristic of plant glycosyltransferases. Biochemical assays demonstrated that all four recombinant proteins catalyzed the glycosylation of emodin to form emodin-6-O-β-D-glucoside, with RpUGT23 exhibiting the highest catalytic efficiency (kcat/Km = 101.51 mM-1 s-1). Optimal biocatalysis was achieved at 35 °C and pH 7.5, with the addition of Mg2+ significantly enhancing enzymatic activity. Substrate specificity profiling further revealed that RpUGT23 possesses catalytic plasticity, effectively glycosylating various flavone and coumarin derivatives. Molecular docking and site-directed mutagenesis identified critical amino acid residues (e.g., His19, Thr381, Gln383, and Trp361) and confirmed the essential role of the conserved PSPG motif in mediating sugar donor recognition and binding. Collectively, these findings elucidate the molecular framework of anthraquinone glycoside biosynthesis in R. palmatum and provide robust genetic resources for the metabolic engineering of bioactive glycosides in medicinal and functional food plants.
PMID:42019853 | DOI:10.1016/j.ijbiomac.2026.152149