Mechanism of gallic acid biosynthesis in bacteria (Escherichia coli) and walnut (Juglans regia)

Muir, Ryann M and Ibanez, Ana M and Uratsu, Sandra L and Ingham, Elizabeth S and Leslie, Charles A and McGranahan, Gale H and Batra, Neelu and Goyal, Sham and Joseph, Jorly and Jemmis, Eluvathingal D and Dandekar, Abhaya M (2011) Mechanism of gallic acid biosynthesis in bacteria (Escherichia coli) and walnut (Juglans regia). In: Plant Molecular Biology, 75 (6). pp. 555-565.

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Abstract

Gallic acid (GA), a key intermediate in the synthesis of plant hydrolysable tannins, is also a primary anti-inflammatory, cardio-protective agent found in wine, tea, and cocoa. In this publication, we reveal the identity of a gene and encoded protein essential for GA synthesis. Although it has long been recognized that plants, bacteria, and fungi synthesize and accumulate GA, the pathway leading to its synthesis was largely unknown. Here we provide evidence that shikimate dehydrogenase (SDH), a shikimate pathway enzyme essential for aromatic amino acid synthesis, is also required for GA production. Escherichia coli (E. coli) aroE mutants lacking a functional SDH can be complemented with the plant enzyme such that they grew on media lacking aromatic amino acids and produced GA in vitro. Transgenic Nicotiana tabacum lines expressing a Juglans regia SDH exhibited a 500% increase in GA accumulation. The J. regia and E. coli SDH was purified via overexpression in E. coli and used to measure substrate and cofactor kinetics, following reduction of NADP(+) to NADPH. Reversed-phase liquid chromatography coupled to electrospray mass spectrometry (RP-LC/ESI-MS) was used to quantify and validate GA production through dehydrogenation of 3-dehydroshikimate (3-DHS) by purified E. coli and J. regia SDH when shikimic acid (SA) or 3-DHS were used as substrates and NADP(+) as cofactor. Finally, we show that purified E. coli and J. regia SDH produced GA in vitro.

Item Type:	Journal Article
Publication:	Plant Molecular Biology
Publisher:	Springer
Additional Information:	Copyright of this article belongs to Springer.
Keywords:	AroE;Gallic acid;Juglans regia;Escherichia coli;Shikimate dehydrogenase;Walnut;Tannins
Department/Centre:	Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited:	12 Apr 2011 10:12
Last Modified:	12 Apr 2011 10:12
URI:	http://eprints.iisc.ac.in/id/eprint/36567

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