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Michlmayr, H; Varga, E; Lupi, F; Malachová, A; Hametner, C; Berthiller, F; Adam, G; .
(2017): Synthesis of Mono- and Di-Glucosides of Zearalenone and α-/β-Zearalenol by Recombinant Barley Glucosyltransferase HvUGT14077.
Toxins (Basel). 2017; 9(2): FullText FullText_BOKU

Abstract:: Zearalenone (ZEN) is an estrogenic mycotoxin occurring in Fusarium-infected cereals. Glucosylation is an important plant defense mechanism and generally reduces the acute toxicity of mycotoxins to humans and animals. Toxicological information about ZEN-glucosides is limited due to the unavailability of larger amounts required for animal studies. HvUGT14077, a recently-validated ZEN-conjugating barley UDP-glucosyltransferase was expressed in Escherichia coli, affinity purified, and characterized. HvUGT14077 possesses high affinity (K-m = 3 mu M) and catalytic efficiency (k(cat)/K-m = 190 s(-1.)mM(-1)) with ZEN. It also efficiently glucosylates the phase-I ZEN-metabolites alpha-zearalenol and beta-zearalenol, with k(cat)/K-m of 40 and 74 s(-1.)mM(-1), respectively. HvUGT14077 catalyzes O-glucosylation at C-14 and C-16 with preference of 14-glucoside synthesis. Furthermore, relatively slow consecutive formation of 14,16-di-glucosides was observed; their structures were tentatively identified by mass spectrometry and for ZEN-14,16-di-glucoside confirmed by nuclear magnetic resonance spectroscopy. Recombinant HvUGT14077 allowed efficient preparative synthesis of ZEN-glucosides, yielding about 90% ZEN-14-glucoside and 10% ZEN-16-glucoside. The yield of ZEN-16-glucoside could be increased to 85% by co-incubation with a beta-glucosidase highly selective for ZEN-14-glucoside. Depletion of the co-substrate UDP-glucose was counteracted by a sucrose synthase based regeneration system. This strategy could also be of interest to increase the yield of minor glucosides synthesized by other glucosyltransferases.
Authors BOKU Wien:: Adam Gerhard; Berthiller Franz; Malachova Alexandra; Michlmayr Herbert; Varga Elisabeth
Find related publications in this database (using NML MeSH Indexing): Escherichia coli/genetics;Glucosides/chemistry;Glucosides/metabolism*;Glucosyltransferases/genetics;Glucosyltransferases/metabolism*;Hordeum/enzymology;Molecular Structure;Plant Proteins/genetics;Plant Proteins/metabolism*;Recombinant Fusion Proteins/metabolism;Zearalenone/metabolism*;
Find related publications in this database (Keywords): zearalenone-14-glucoside; zearalenone-16-glucoside; masked mycotoxin; glycosylation; sucrose synthase; secondary metabolite