Instituto de la Grasa (CSIC), Seville, Spain.
Phytochemistry. 2010 Jun;71(8-9):860-9. doi: 10.1016/j.phytochem.2010.03.015. Epub 2010 Apr 9.
Acyl-acyl carrier protein (ACP) thioesterases are enzymes that terminate the intraplastidial fatty acid synthesis in plants by hydrolyzing the acyl-ACP intermediates and releasing free fatty acids to be incorporated into glycerolipids. These enzymes are classified in two families, FatA and FatB, which differ in amino acid sequence and substrate specificity. In the present work, both FatA and FatB thioesterases were cloned, sequenced and characterized from castor (Ricinus communis) seeds, a crop of high interest in oleochemistry. Single copies of FatA and FatB were found in castor resulting to be closely related with those of Jatropha curcas. The corresponding mature proteins were heterologously expressed in Escherichia coli for biochemical characterization after purification, resulting in high catalytic efficiency of RcFatA on oleoyl-ACP and palmitoleoyl-ACP and high efficiencies of RcFatB for oleoyl-ACP and palmitoyl-ACP. The expression profile of these genes displayed the highest levels in expanding tissues that typically are very active in lipid biosynthesis such as developing seed endosperm and young expanding leaves. The contribution of these two enzymes to the synthesis of castor oil is discussed.
酰基辅酶 A（ACP）硫酯酶是一类能够终止植物细胞内脂肪酸合成的酶，通过水解酰基辅酶 A 中间产物，释放游离脂肪酸并将其整合到甘油脂质中。这些酶分为 FatA 和 FatB 两个家族，它们在氨基酸序列和底物特异性上有所不同。在本研究中，我们从蓖麻（Ricinus communis）种子中克隆、测序并鉴定了 FatA 和 FatB 硫酯酶，蓖麻是油脂化学中具有重要意义的作物。结果表明，蓖麻中存在单拷贝的 FatA 和 FatB，与麻疯树（Jatropha curcas）的亲缘关系较近。成熟蛋白经纯化后在大肠杆菌中异源表达进行生化特性分析，结果表明 RcFatA 对油酰-ACP 和棕榈油酸酰-ACP 具有较高的催化效率，RcFatB 对油酰-ACP 和棕榈酰-ACP 具有较高的效率。这些基因的表达谱显示，在种子胚乳和幼叶等典型的脂质生物合成活跃的扩张组织中表达水平最高。讨论了这两种酶对蓖麻油合成的贡献。
