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Download fileAn Ambidextrous Polyphenol Glycosyltransferase PaGT2 from Phytolacca americana
journal contribution
posted on 2020-07-02, 18:04 authored by Rakesh Maharjan, Yohta Fukuda, Naomichi Shimomura, Taisuke Nakayama, Yuta Okimoto, Koki Kawakami, Toru Nakayama, Hiroki Hamada, Tsuyoshi Inoue, Shin-ichi OzakiThe
glycosylation of small hydrophobic compounds is catalyzed by
uridine diphosphate glycosyltransferases (UGTs). Because glycosylation
is an invaluable tool for improving the stability and water solubility
of hydrophobic compounds, UGTs have attracted attention for their
application in the food, cosmetics, and pharmaceutical industries.
However, the ability of UGTs to accept and glycosylate a wide range
of substrates is not clearly understood due to the existence of a
large number of UGTs. PaGT2, a UGT from Phytolacca
americana, can regioselectively glycosylate piceatannol but
has low activity toward other stilbenoids. To elucidate the substrate
specificity and catalytic mechanism, we determined the crystal structures
of PaGT2 with and without substrates and performed
molecular docking studies. The structures have revealed key residues
involved in substrate recognition and suggest the presence of a nonconserved
catalytic residue (His81) in addition to the highly conserved catalytic
histidine in UGTs (His18). The role of the identified residues in
substrate recognition and catalysis is elucidated with the mutational
assay. Additionally, the structure-guided mutation of Cys142 to other
residues, Ala, Phe, and Gln, allows PaGT2 to glycosylate
resveratrol with high regioselectivity, which is negligibly glycosylated
by the wild-type enzyme. These results provide a basis for tailoring
an efficient glycosyltransferase.