Functional specialization of two UDP‐glycosyltransferases MpUGT735A2 and MpUGT743A1 in the liverworts Marchantia polymorpha

Abstract

Family 1 UDP‐glycosyltransferases (UGTs) are known to glycosylate multiple secondary plant metabolites and have been extensively studied. The increased availability of plant genome resources allows the identification of wide gene families, both functional and organizational. In this investigation, two MpUGT isoforms were cloned and functionally characterized from liverworts marchantia polymorpha and had high glycosylation activity against several flavonoids. MpUGT735A2 protein, in particular, tolerates a wide spectrum of substrates (flavonols, flavanones, flavones, stilbenes, bibenzyls, dihydrochalcone, phenylpropanoids, xanthones, and isoflavones). Overexpression of MpUGT735A2 and MpUGT743A1 in Arabidopsis thaliana enhances the accumulation of 3‐O‐glycosylated flavonol (kaempferol 3‐O‐glucoside‐7‐O‐rhamnose), consistent with its in vitro enzymatic activity. Docking and mutagenesis techniques were applied to identify the structural and functional properties of MpUGT735A2 with promiscuous substrates. Mutation of Pro87 to Ser, or Gln88 to Val, substantially altered the regioselectivity for luteolin glycosylation, predominantly from the 3′‐O‐ to the 7‐O‐position. The results were elucidated by focusing on the novel biocatalysts designed for producing therapeutic flavonoids. This investigation provides an approach to modulate MpUGT735A2 as a candidate gene for diverse glycosylation catalysis and a tool to design GTs with new substrate specificities for biomedical applications.

Efficient Production of Flavonoid Glucuronides in Escherichia coli Using Flavonoid O-Glucuronosyltransferases Characterized from Marchantia polymorpha

“…Our group recently characterized two UGTs with strong glycosyl transfer activity from UDP-Glc to flavonoid aglycones. However, UDP-GA was inert as a sugar donor in the in vitro activity analysis of the two UGTs . To characterize the UGATs responsible for the biosynthesis of flavonoid glucuronides, in the present investigation, we screened the M. polymorpha genomes and characterized two other UGTs, MpUGT742A1 and MpUGT736B1, which showed high catalytic activity with UDP-GA as a sugar donor.…”

“…However, UDP-GA was inert as a sugar donor in the in vitro activity analysis of the two UGTs. 24 To characterize the UGATs responsible for the biosynthesis of flavonoid glucuronides, in the present investigation, we screened the M. polymorpha genomes and characterized two other UGTs, MpUGT742A1 and MpUGT736B1, which showed high catalytic activity with UDP-GA as a sugar donor. These two enzymes accepted various flavonoids as substrates and catalyzed glucuronidation at different sites with high conversion rates.…”