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ISHS Acta Horticulturae 381: International Symposium on Natural Phenols in Plant Resistance

IN VITRO-STUDIES ON THE BIOSYNTHESIS OF GALLOTANNINS AND ELLAGITANNINS

Author:   Georg G. Gross
DOI:   10.17660/ActaHortic.1994.381.3
Abstract:
The biosynthesis of hydrolyzable tannins (i.e. gallotannins and ellagitannins) was studied with enzyme preparations from Quercus robur, Q. rubra, Rhus typhina and Tellima grandiflora. The primary metabolite beta-glucogallin (1-O-beta-D-glucose), formed from free gallic acid and UDP-glucose, was also found to serve as the principal acyl donor in the subsequent step-wise conversion of this mono-ester to 1,2,3,4,6-penta-O-galloyl-beta-D-glucose, the common precursor of both gallotannins and ellagitannins. Gallotannins were formed by the continuation of this reaction principle, while ellagitannins were synthesized by oxidation of pentagalloylglucose in the presence of a novel FMN-dependent enzyme. In addition, also counter-directed catabolic processes appear to occur in higher plants as indicated by the discovery of a tannase-like hydrolase.

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