An antibacterial pyrazole derivative from Burkholderia glumae, a bacterial pathogen of rice.
Burkholderia glumae, a bacterial pathogen on rice, produced compounds in liquid culture that, in agar diffusion assays, gave strong inhibitory action against Erwinia amylovora, the bacterium responsible for fire blight disease of apple and pear trees. Products were isolated from culture medium by cation exchange and then purified by bioassay-guided chromatographic methods. Two major products were obtained, one of which was not active when fully purified. Each product showed a single ninhydrin-staining spot on TLC and a single HPLC peak. The non-active product was deduced from NMR, MS, and chemical data, to be the tripeptide L-alanyl-L-homoserinyl-L-aspartate. The NMR data for the active product demonstrated that it contained the same tripeptide, but functionalised at the beta-carboxyl of the C-terminal aspartate, by a moiety that provided an additional 98 mass units to the parent tripeptide. Various data led to the interpretation that this moiety was a highly unusual oxygenated pyrazole structure, and thus the bioactive product was deduced to be 3-[L-alanyl-L-homoserinyl-L-aspartyl-beta-carboxy]-4-hydroxy-5-oxopyrazole. This compound was found to inhibit the growth of a number of different bacterial species.
The Horticulture and Food Research Institute of New Zealand Limited, Plant Pathogen Interactions, 120 Mt. Albert Road, Private Bag 92169, Auckland 1025, New Zealand. rmitchell@hortresearch.co.nz
Robin E
RE
Mitchell
David R
DR
Greenwood
Vijayalekshmi
V
Sarojini
D000900:Anti-Bacterial Agents / Q000096:biosynthesis / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology*; D019117:Burkholderia / Q000737:chemistry*; D044084:Erwinia amylovora / Q000187:drug effects; D009842:Oligopeptides / Q000737:chemistry; D012275:Oryza / Q000382:microbiology*; D011720:Pyrazoles / Q000737:chemistry* / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*
D000900:Anti-Bacterial Agents; D009842:Oligopeptides; D011720:Pyrazoles; C031280:pyrazole