脂肪酸生物合成途径的 β-酮酰基酰基载体蛋白还原酶 (FabG) 活性是 3-氧代-高丝氨酸内酯酰基链长度的决定因素,Microbiology

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脂肪酸生物合成途径的 β-酮酰基酰基载体蛋白还原酶 (FabG) 活性是 3-氧代-高丝氨酸内酯酰基链长度的决定因素
Microbiology ( IF 1.3 ) Pub Date : 2002-12-01 , DOI: 10.1099/00221287-148-12-3849
Tung T. Hoang ₁ , Sarah A. Sullivan ₁ , John K. Cusick ₁ , Herbert P. Schweizer ₁

Affiliation

群体感应需要两种酰基高丝氨酸内酯 (AHL) N-(丁酰基)-L-高丝氨酸内酯和 N-[3-氧代十二烷酰基]-L-高丝氨酸内酯 (3-oxo-C(12)-HSL)铜绿假单胞菌。这些 AHL 的不变内酯环来自 S-腺苷甲硫氨酸，可变酰基链来自细胞酰基-酰基载体蛋白 (ACP) 池。该反应由表现出酰基链特异性的特定 AHL 合酶催化。铜绿假单胞菌的培养上清液含有多个 3-oxo-AHL，它们的酰基链长度不同，但它们的生理作用（如果有的话）仍然未知。利用纯化的铜绿假单胞菌 Fab 蛋白、ACP 和 LasI 3-oxo-AHL 合成酶建立了体外脂肪酸-3-oxo-AHL 合成系统。在过量蛋白质、底物和辅因子存在的情况下，该系统几乎只生产 3-oxo-C(12)-HSL。当 β-酮酰基-ACP 还原酶 (FabG) 催化步骤通过从首选的 NADPH 辅因子转换为 NADH 进行限速时，产生的短链 3-氧代-AHL 水平增加，可能是因为短链酮酰基-ACP 积累从而成为 LasI 衬底。与这些体外观察结果一致，fabG(Ts) 突变体在体内产生了增加的 3-oxo-AHLs。因此，体外和体内证据表明脂肪酸生物合成途径的 FabG 活性的调节可能决定这些 3-oxo-AHL 的酰基链长度，并且 LasI 3-oxo-AHL 合酶足以合成它们。产生的短链 3-oxo-AHLs 水平增加，可能是因为短链 ketoacyl-ACPs 积累并因此成为 LasI 底物。与这些体外观察结果一致，fabG(Ts) 突变体在体内产生了增加的 3-oxo-AHLs。因此，体外和体内证据表明脂肪酸生物合成途径的 FabG 活性的调节可能决定这些 3-oxo-AHL 的酰基链长度，并且 LasI 3-oxo-AHL 合酶足以合成它们。产生的短链 3-oxo-AHLs 水平增加，可能是因为短链 ketoacyl-ACPs 积累并因此成为 LasI 底物。与这些体外观察结果一致，fabG(Ts) 突变体在体内产生了增加的 3-oxo-AHLs。因此，体外和体内证据表明脂肪酸生物合成途径的 FabG 活性的调节可能决定这些 3-oxo-AHL 的酰基链长度，并且 LasI 3-oxo-AHL 合酶足以合成它们。

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β-Ketoacyl acyl carrier protein reductase (FabG) activity of the fatty acid biosynthetic pathway is a determining factor of 3-oxo-homoserine lactone acyl chain lengths

The two acyl-homoserine lactones (AHLs) N-(butyryl)-L-homoserine lactone and N-[3-oxododecanoyl]-L-homoserine lactone (3-oxo-C(12)-HSL) are required for quorum sensing in Pseudomonas aeruginosa. These AHLs derive their invariant lactone rings from S-adenosylmethionine and their variable acyl chains from the cellular acyl-acyl carrier protein (ACP) pool. This reaction is catalysed by specific AHL synthases, which exhibit acyl chain specificity. Culture supernatants of P. aeruginosa contain multiple 3-oxo-AHLs that differ in their acyl chain lengths but their physiological role, if any, remains unknown. An in vitro fatty acid-3-oxo-AHL synthesis system was established utilizing purified P. aeruginosa Fab proteins, ACP and the LasI 3-oxo-AHL synthase. In the presence of excess protein, substrates and cofactors, this system produced almost exclusively 3-oxo-C(12)-HSL. When the beta-ketoacyl-ACP reductase (FabG) catalysed step was made rate-limiting by switching from the preferred NADPH cofactor to NADH, increased levels of short chain 3-oxo-AHLs were produced, presumably because shorter-chain ketoacyl-ACPs accumulated and thus became LasI substrates. Consistent with these in vitro observations, a fabG(Ts) mutant produced increased amounts of 3-oxo-AHLs in vivo. Thus, in vitro and in vivo evidence indicated that modulation of FabG activity of the fatty acid biosynthetic pathway may determine the acyl chain lengths of these 3-oxo-AHLs and that the LasI 3-oxo-AHL synthase is sufficient for their synthesis.

更新日期：2002-12-01

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