Tandem UGT71B5s Catalyze Lignan Glycosylation in Isatis indigotica With Substrates Promiscuity

Xiao Chen,Lei Zhang,Junfeng Chen,Shunuo Li,Jingxian Feng,Wansheng Chen,Yong Diao,Yun Wang,Ying Xiao

doi:10.3389/fpls.2021.637695

Abstract

Lignans are a class of chemicals formed by the combination of two molecules of phenylpropanoids with promising nutritional and pharmacological activities. Lignans glucosides, which are converted from aglycones catalyzed by uridine diphosphate (UDP) glycosyltransferases (UGTs), have abundant bioactivities. In the present study, two UGTs from Isatis indigotica Fort., namely IiUGT71B5a and IiUGT71B5b, were characterized to catalyze the glycosylation of lignans with promiscuities toward various sugar acceptors and sugar donors, and pinoresinol was the preferred substrate. IiUGT71B5a was capable of efficiently producing both pinoresinol monoglycoside and diglycoside. However, IiUGT71B5b only produced monoglycoside, and exhibited considerably lower activity than IiUGT71B5a. Substrate screening indicated that ditetrahydrofuran is the essential structural characteristic for sugar acceptors. The transcription of IiUGT71B5s was highly consistent with the spatial distribution of pinoresinol glucosides, suggesting that IiUGT71B5s may play biological roles in the modification of pinoresinol in I. indigotica roots. This study not only provides insights into lignan biosynthesis, but also elucidates the functional diversity of the UGT family.

Highlights

Lignans, with a wide variety of clinically and dietarily important biological activities (Milder et al, 2005; Saarinen et al, 2007; Wang et al, 2011; Shi et al, 2012; Satake et al, 2013; Nantarat et al, 2020), are a class of derivatives formed by the combination of two molecules of phenylpropanoids (Fang and Hu, 2018)
Matairesinol can be continuely converted into (−)-deoxypodophyllotoxin by cytochrome P450s (CYPs), O-methyltransferases (OMTs), and 2-oxoglutarate/Fe(II)dependent dioxygenase (2-ODD), and hydroxylated by CYPs to produce (−)-4'-desmethyl-epipodophyllotoxin in S. hexandrum (Lau and Sattely, 2015). In another lignan biosynthesis pathway that mainly occurs in the seeds of S. indicum, pinoresinol can be catalyzed by CYP81Q1 to sequentially generate piperitol and sesamin, sesamin can be converted into sesamolin and sesaminol (Murata et al, 2017; Ono et al, 2020)
Given that sesaminol does not exist in I. indigotica, we proposed that IiUGT71B5a is the major UGT contributing to the biosynthesis of pinoresinol glucosides

Summary

Introduction

With a wide variety of clinically and dietarily important biological activities (Milder et al, 2005; Saarinen et al, 2007; Wang et al, 2011; Shi et al, 2012; Satake et al, 2013; Nantarat et al, 2020), are a class of derivatives formed by the combination of two molecules of phenylpropanoids (Fang and Hu, 2018). Matairesinol can be continuely converted into (−)-deoxypodophyllotoxin by cytochrome P450s (CYPs), O-methyltransferases (OMTs), and 2-oxoglutarate/Fe(II)dependent dioxygenase (2-ODD), and hydroxylated by CYPs to produce (−)-4'-desmethyl-epipodophyllotoxin in S. hexandrum (Lau and Sattely, 2015). In another lignan biosynthesis pathway that mainly occurs in the seeds of S. indicum, pinoresinol can be catalyzed by CYP81Q1 to sequentially generate piperitol and sesamin, sesamin can be converted into sesamolin and sesaminol (Murata et al, 2017; Ono et al, 2020). Lignans are usually glycosylated by uridine diphosphate (UDP) glycosyltransferases (UGTs), and stored stably in plant cells (Lorenc-Kukula et al, 2005; Hano et al, 2006; Ono et al, 2010, 2020; Ghose et al, 2014; Teponno et al, 2016; Murata et al, 2017)

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Conclusion