作者:Antje Klempien、Yasuhisa Kaminaga、Anthony Qualley、Dinesh A. Nagegowda、Joshua R. Widhalm、Irina Orlova、Ajit Kumar Shasany、Goro Taguchi、Christine M. Kish、Bruce R. Cooper、John C. D’Auria、David Rhodes、Eran Pichersky、Natalia Dudareva
DOI:10.1105/tpc.112.097519
日期:2012.5
Biosynthesis of benzoic acid from Phe requires shortening of the side chain by two carbons, which can occur via the β-oxidative or nonoxidative pathways. The first step in the β-oxidative pathway is cinnamoyl-CoA formation, likely catalyzed by a member of the 4-coumarate:CoA ligase (4CL) family that converts a range of trans-cinnamic acid derivatives into the corresponding CoA thioesters. Using a functional genomics approach, we identified two potential CoA-ligases from petunia (Petunia hybrida) petal-specific cDNA libraries. The cognate proteins share only 25% amino acid identity and are highly expressed in petunia corollas. Biochemical characterization of the recombinant proteins revealed that one of these proteins (Ph-4CL1) has broad substrate specificity and represents a bona fide 4CL, whereas the other is a cinnamate:CoA ligase (Ph-CNL). RNA interference suppression of Ph-4CL1 did not affect the petunia benzenoid scent profile, whereas downregulation of Ph-CNL resulted in a decrease in emission of benzylbenzoate, phenylethylbenzoate, and methylbenzoate. Green fluorescent protein localization studies revealed that the Ph-4CL1 protein is localized in the cytosol, whereas Ph-CNL is in peroxisomes. Our results indicate that subcellular compartmentalization of enzymes affects their involvement in the benzenoid network and provide evidence that cinnamoyl-CoA formation by Ph-CNL in the peroxisomes is the committed step in the β-oxidative pathway.
苯丙氨酸生物合成过程中,苯甲酸侧链需要缩短两个碳原子,这可以通过β-氧化或非氧化途径实现。β-氧化途径的第一步是形成肉桂酰-CoA,这很可能是由4-香豆酸:CoA连接酶(4CL)家族中的一员催化完成的,该酶可将一系列反式肉桂酸衍生物转化为相应的硫代酯CoA。我们采用功能基因组学方法,从矮牵牛(Petunia hybrida)花瓣特异性cDNA文库中鉴定出两种潜在的CoA连接酶。同源蛋白的氨基酸相似度仅为25%,在矮牵牛花冠中高度表达。重组蛋白的生化特性表明,其中一种蛋白(Ph-4CL1)具有广泛的底物特异性,是真正的4CL,而另一种是肉桂酰:CoA连接酶(Ph-CNL)。RNA干扰抑制Ph-4CL1不会影响矮牵牛的苯类气味,而下调Ph-CNL会导致苄基苯甲酸酯、苯乙基苯甲酸酯和甲基苯甲酸酯的释放减少。绿色荧光蛋白定位研究表明,Ph-4CL1蛋白定位于细胞质中,而Ph-CNL定位于过氧化物酶体中。我们的结果表明,酶的亚细胞区室化会影响它们在苯类网络中的参与,并提供了证据表明,Ph-CNL在过氧化物酶体中