Abstract
Aurone glycosides display a variety of biological activities. However, reports about glycosyltransferases (GTs) responsible for aurones glycosylation are limited. Here, the transcriptome-wide discovery and identification of an aurone glycosyltransferase with glycosidase activity is reported. Specifically, a complementary DNA (cDNA), designated as OsUGT1, was isolated from the plant Ornithogalum saundersiae based on transcriptome mining. Conserved domain (CD)-search speculated OsUGT1 as a flavonoid GT. Phylogenetically, OsUGT1 is clustered as the same phylogenetic group with a putative 5,6-dihydroxyindoline-2-carboxylic acid (cyclo-DOPA) 5-O-glucosyltransferase, suggesting OsUGT1 may be an aurone glycosyltransferase. The purified OsUGT1 was therefore used as a biocatalyst to incubate with the representative aurone sulfuretin. In vitro enzymatic analyses showed that OsUGT1 was able to catalyze sulfuretin to form corresponding monoglycosides, suggesting OsUGT1 was indeed an aurone glycosyltransferase. OsUGT1 was observed to be a flavonoid GT, specific for flavonoid substrates. Moreover, OsUGT1 was demonstrated to display transglucosylation activity, transferring glucosyl group to sulfuretin via o-Nitrophenyl-β-d-glucopyranoside (oNP-β-Glc)-dependent fashion. In addition, OsUGT1-catalyzed hydrolysis was observed. This multifunctionality of OcUGT1 will broaden the application of OcUGT1 in glycosylation of aurones and other flavonoids.
Highlights
Aurones, represented by sulfuretin (Figure 1, 1) and sulfurein (Figure 1, 1c), are minor tricyclic flavonoids that consist of a benzofuranone ring linked through a carbon-carbon double bond to a phenyl moiety (Figure 1) [1]
In vitro enzymatic analyses showed that OsUGT1 was able to catalyze sulfuretin to form corresponding monoglycosides, suggesting OsUGT1 was an aurone glycosyltransferase
The cell-free supernatant containing the recombinant OsUGT1 or the purified OsUGT1 was used as a biocatalyst for glycosylation reaction, which was performed at 37 ◦ C for 60 min in 100 μL of 20 mM
Summary
Aurones, represented by sulfuretin (Figure 1, 1) and sulfurein (Figure 1, 1c), are minor tricyclic flavonoids that consist of a benzofuranone ring linked through a carbon-carbon double bond to a phenyl moiety (Figure 1) [1]. OsUGT1-catalyzed biosynthesis ofof sulfuretin or transglucosylation reaction.UDP: UDP:uridine uridinediphosphate; diphosphate;OsUGT1: OsUGT1: glycosyltransferase glycosyltransferase from or transglucosylation reaction Among these modifications, glycosylation of aurones have attracted much interest because. The as OsUGT1, coding for an aurone GT was firstly isolated from Ornithogalum saundersiae based recombinant OsUGT1 was determined to have the ability to glucosylate sulfuretin (1) to form on transcriptome mining. OsUGT1 was demonstrated activity, forming sulfuretin glucosides using cheap aryl glycosides as sugar donor by to display transglycosylase activity,OsUGT1-catalyzed forming sulfuretinhydrolysis glucosidesactivity using cheap glycosides as transglycosylation. Thisand multifunctionality other flavonoids. broadened the potential applications of OsUGT1 in glycosylation of aurones and other flavonoids
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