The human pathogen Pseudomonas aeruginosa uses N-butyryl-L-homoserine lactone (BHL) and N-(3-oxododecanyl)-L-homoserine lactone (OdDHL) as small molecule intercellular signals in a phenomenon known as quorum sensing (QS). QS modulators are effective at attenuating P. aeruginosa virulence; therefore, they are a potential new class of antibacterial agent. The lactone in BHL and OdDHL is hydrolysed under physiological conditions. The hydrolysis proceeds at a rate faster than racemisation of the α-chiral centre. Non-hydrolysable, non-racemic analogues (small molecule probes) were designed and synthesised, replacing the lactone with a ketone. OdDHL analogues were found to be relatively unstable to decomposition unless they were difluorinated between the β-keto amide. Stability studies on a non-hydrolysable, cyclohexanone analogue indicated that racemisation of the α-chiral centre was relatively slow. This analogue was assayed to show that the L-isomer is likely to be responsible for the QS autoinducing activity in P. aeruginosa and Serratia strain ATCC39006.
人类病原体
铜绿假单胞菌(Pseudomonas aeruginosa)利用N-丁酰基-
L-高丝氨酸内
酯(BHL)和N-(3-
氧代
十二烷基)-
L-高丝氨酸内
酯(OdDHL)作为小分子细胞间信号,这种现象被称为群体感应(Quorum sensing,QS)。QS调节剂能有效减弱
铜绿假单胞菌的毒力,因此,它们有可能成为一类新型抗菌剂。在生理条件下,BHL和OdDHL中的内
酯环会发生
水解,且
水解速率快于α-手性中心的消旋化。设计并合成了非
水解、非消旋的类似物(小分子探针),用
酮基取代了内
酯环。研究发现,除非在β-
酮胺基之间进行二
氟化,否则OdDHL类似物相对不稳定,易于分解。对一种非
水解的
环己酮类似物的稳定性研究显示,α-手性中心的消旋化相对较慢。该类似物的检测结果表明,L-异构体可能是
铜绿假单胞菌和沙雷氏菌A
TCC39006株中QS自诱导活性的原因。