Martin-Luther-Universität Halle-Wittenberg

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Assoziiertes Forschungsprojekt: Pflanzlicher Gallotanninstoffwechsel

Enzymes of plant gallotannin metabolism

Carsten Milkowski (IZN, MLU)

The accumulation of gallotannins has been documented as a prevalent  chemical trait in a range of dicotyledonous plants and simple green  algae. Gallotannins, potent protein-complexing polyphenols, form  part of the chemical defense against microbial pathogens and herbivores.  The biosynthesis of gallotannins depends on the formation of gallic  acid and a series of acyltransfer reactions to yield 1,2,3,4,6-penta-O-galloylglucose. In this project we will use homology-based  cloning approaches to isolate cDNAs encoding the essential enzymes of  this metabolic pathway - dehydroshikimate dehydrogenase, UDP  glucose:gallic acid glucosyltransferase and a group of position-specific  galloyl transferases, which employ the β-acetal ester 1-O-galloylglucose as acyl donor. The galloyltransferases form a novel group of plant acyltransferases related to β-glucosidase-like hydrolases. By site-directed  mutagenesis and kinetic characterization of the reaction mechanism the  molecular determinants of galloyltransferase activity will be  elucidated. The identified sequences will be exploited to transfer the  complex gallotannin metabolic pathway to model organisms with the long-term  goals to increase plant pathogen resistance and to implement the  production of tailored gallotannins for industrial application.

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