Identification and characterization of a promiscuous pentacyclic triterpenoid O-glycosyltransferase from Phytolacca americana

Abstract

Glycosyltransferases (GTs) are key enzymes in the glycosylation of plant secondary metabolites, primarily catalyzing the transfer of a sugar moiety from an activated donor to a specific acceptor molecule. Triterpenoid saponins, an abundant and diverse group of natural products, are composed of triterpenoid aglycones and one or more sugar chains, under the catalysis of GTs. Phytolacca Radix is a traditional Chinese medicine containing over 40 triterpenoid saponins with pharmacological values. However, the identification of glycosyltransferases related to triterpenoid saponin synthesis from Phytolacca species remains scarce. In this study, a novel glycosyltransferase, PamUGT, was identified from Phytolacca americana. PamUGT exhibits catalytic activity toward 28-/30-COOH of pentacyclic triterpenoids, and it exhibits a preference for the C-30 position when both carboxyl groups are available. To our knowledge, PamUGT is the first glycosyltransferase identified in Phytolacca species that can catalyze triterpenoids. Further analysis of substrate specificity revealed that PamUGT catalyzes the glycosylation of a wide range of compounds, including triterpenoids, flavonoids, diterpenoids, alkaloids, and phenolic acids. Our findings identify a highly promiscuous glycosyltransferase, offering a valuable enzymatic tool for modifying diverse natural products.

Keywords

Phytolacca americana / Pentacyclic triterpenoid / Glycosylation / Glycosyltransferase

Funding

This study was supported by the National Natural Science Foundation of China (No. 82304667) and the Science and Technology Commission of Shanghai Municipality (No. Shanghai Sailing Program 23YF1457800).

Declaration of competing interest

All authors declare that there are no conflicts of interest.

Supporting information

The supporting information for this article, including NMR spectra of products 1a, 2a, and 9a, TIC spectra of the PamUGT-catalyzed reaction of compounds 3−42, and UPLC/Q-TOF-MS data of 4a−42a, can be obtained by contacting the corresponding authors via E-mail.

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