TY - JOUR
T1 - Glycosylated triterpenoid saponin
T2 - A specific inhibitor of diguanylate cyclase from Acetobacter xylinum. Biological activity and distribution
AU - Ohana, Patricia
AU - Delmer, Deborah P.
AU - Volman, Gail
AU - Benziman, Moshe
PY - 1998/2
Y1 - 1998/2
N2 - 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-diGMP 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. Similarly, digitonin permeabilized tobacco cell cultures display inhibition of glucan synthesis in the presence of GTS.
AB - 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-diGMP 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. Similarly, digitonin permeabilized tobacco cell cultures display inhibition of glucan synthesis in the presence of GTS.
KW - Acetobacter xylinum
KW - c-di-GMP
KW - dgc
KW - GTS
KW - Pisum sativum
UR - http://www.scopus.com/inward/record.url?scp=0031887037&partnerID=8YFLogxK
U2 - 10.1093/oxfordjournals.pcp.a029352
DO - 10.1093/oxfordjournals.pcp.a029352
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AN - SCOPUS:0031887037
SN - 0032-0781
VL - 39
SP - 153
EP - 159
JO - Plant and Cell Physiology
JF - Plant and Cell Physiology
IS - 2
ER -