Glycosylation, the process by which sugar molecules are attached to other compounds, plays a vital role in shaping the structure, stability and biological activity of countless natural products. Plant-derived uridine diphosphate-dependent glycosyltransferases (UGTs) are key catalysts of this process, and understanding how they achieve their remarkable specificity has long been a central goal in enzymology. A research team has now resolved the structural basis for substrate recognition and catalysis in PamUGT, a glycosyltransferase from pokeweed (Phytolacca americana), offering a detailed blueprint for engineering these versatile biocatalysts.

Using X-ray crystallography, the researchers solved multiple structures of PamUGT, including its complexes with the sugar donor UDP-glucose and various acceptor molecules. These structures revealed how the enzyme’s active site is architecturally organized to accommodate both the sugar donor and a wide range of acceptor substrates, a hallmark of UGT enzymes that makes them attractive tools for biotechnology.

The team identified a network of key amino acid residues that govern substrate binding and catalytic efficiency. Through site-directed mutagenesis, they demonstrated that altering specific residues in the acceptor-binding pocket could shift the enzyme’s substrate preference, providing direct evidence for how small structural changes can reshape catalytic function.

These findings not only deepen understanding of plant glycosyltransferase biology but also establish a framework for rationally engineering UGT enzymes with tailored substrate specificities. Because glycosylation can dramatically alter the solubility, stability, and bioactivity of natural products, engineered UGTs hold significant promise for applications in pharmaceutical synthesis, natural product diversification and green chemistry.

By combining structural biology with biochemical validation, the study provides a roadmap for future efforts to harness and redesign plant glycosyltransferases for the targeted production of valuable glycosylated compounds.

Journal: Horticulture Research