| N-acylhomoserine lactone(AHL), as quorum sensing signals, regulate expression of virulence factors of many plant pathogens. The N-acylhomoserine lactone lactonase (AHL-Lactonase) could inactivate AHLs by hydrolyzing the lactone bond to produce corresponding N-acyl homoserines, then blocking the quorum sensing system and attenuating pathogen's virulence.Using glutathione-agarose affinity column and treated with Thrombin, the recombinant AHL-Lactonase with the molecular weight of 28KD was purified. It had a good stability blow 30℃, the optical pH for catalyzing reaction is 8.0, zinc or other metal ions was not required for enzyme activity. Kinetic and specifity analysis showed that AHL-Lactonase had a strong substrate specifity and enzyme activity to all tested three AHLs, and the catalytic efficiency was 3.35, 3.80. 4.92 (mM-1·s-1) respectively, which suggested a broad catalytic spectrum.Many pathogens of animal and plant, such as Erwinia cawtovora pv.carotovora and Pseudomonas aeruginosa, producing some kinds of virulence factors before attacking the host, and most of those virulence factors was modulated by the quorum-sensing system which relys on the secret of some small quorum sensing signals. Virulence test demonstrated that the recombinant AHL-Lactonase has a strong anti-pathogenic activity to Erwinia cawtovora, and the addition of AHL-Lactonase to the medium of pathogen could reduced the activity of pectate lyase, prctin lyase, cellulase and polygalacturonase after 20h.
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