Journal Article

Glycosylated Triterpenoid Saponin: a Specific Inhibitor of Diguanylate Cyclase from <i>Acetobacter xylinum.</i> Biological Activity and Distribution

Patricia Ohana, Deborah P. Delmer, Gail Volman and Moshe Benziman

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 39, issue 2, pages 153-159
Published in print February 1998 | ISSN: 0032-0781
Published online February 1998 | e-ISSN: 1471-9053 | DOI: http://dx.doi.org/10.1093/oxfordjournals.pcp.a029352
Glycosylated Triterpenoid Saponin: a Specific Inhibitor of Diguanylate Cyclase from Acetobacter xylinum. Biological Activity and Distribution

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In a recent paper (Ohana et al. 1998), we described the purification and structural characterization of a novel glycosidic triterpenoid saponin (GTS), a specific inhibitor of diguanylate cyclase (dgc), the key regulatory enzyme of the cellulose synthesizing apparatus of the bacterium Acetobacter xylinum. This compound and an identical or very similar one were isolated from pea (Pisum sativum), and A. xylinum respectively. We now present the effects of GTS on the kinetic properties of dgc. The observed inhibition is non-competitive with respect to the substrate GTP, is decreased by 50% in the presence of 20 μM c-di-GMP, and is not observed in the presence of various detergents. Photo-affinity labeling studies using [32P]c-di-GMP and purified enzyme showed that the inhibitor affects binding of c-di-GMP to dgc. It was ascertained that GTS, or at least a very similar compound, is present in other plant systems. The antibiotic Papulacandin B also inhibits dgc, although less efficiently than GTS (Ki = 70 μM vs. 5 μM). In in situ assays, highly purified GTS inhibits bacterial cellulose synthesis and dgc activity. Similary, digitonin permeabilized tobacco cell cultures display inhibition of glucan synthesis in the presence of GTS.

Keywords: Acetobacter xylinum; c-di-GMP; dgc; GTS; Pisum sativum.

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Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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