Regulation of fatty acid elongation and initiation by acyl acyl carrier protein in Escherichia coli
Regulation of fatty acid elongation and initiation by acyl acyl carrier protein in Escherichia coli
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DOI：
10.1074/jbc.271.4.1833
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发表时间：
1996-01-26
影响因子：
4.8
通讯作者：
Rock, CO
中科院分区：
文献类型：
--
作者：
Heath, RJ;Rock, CO
长链酰基-酰基载体蛋白（酰基-ACP）被认为是脂肪酸生物合成的生理抑制剂，因为硫酯酶过度表达导致酰基-ACP降解，导致组成性的、不受调节的脂肪酸产生。酰基-ACP抑制的生物化学靶点是未知的，这项工作确定了两种对酰基-ACP反馈抑制敏感的生物合成酶。棕榈酰-ACP抑制大肠杆菌无细胞提取物中[C-14]丙二酰-CoA掺入长链脂肪酸。具有β-羟基丁酰-ACP电泳特性的短链酰基-ACP物质随着[C-14]丙二酰-CoA掺入量的总体降低而积累，表明第一个延长周期是酰基-ACP靶向的。分离了体内催化乙酰辅酶A加丙二酰辅酶A的第一轮脂肪酸合成所需的所有蛋白质，并用这些纯化的组分重建第一个脂肪酸延伸循环。对重建系统中单个酶和中间体积累模式的分析表明，在延伸周期中，β-酮脂酰-ACP合成酶III（fabH）和烯酰-ACP还原酶（fabI）启动脂肪酸合成是由长链酰基-ACP减弱的两个步骤。
Long chain acyl-acyl carrier protein (acyl-ACP) has been implicated as a physiological inhibitor of fatty acid biosynthesis since acyl-ACP degradation by thioesterase overexpression leads to constitutive, unregulated fatty acid production. The biochemical targets for acyl-ACP inhibition were unknown, and this work identified two biosynthetic enzymes that were sensitive to acyl-ACP feedback inhibition. Palmitoyl-ACP inhibited the incorporation of [C-14]malonyl-CoA into long chain fatty acids in cell-free extracts of Escherichia coli. A short chain acyl-ACP species with the electrophoretic properties of beta-hydroxybutyryl-ACP accumulated concomitant with the overall decrease in the amount of [C-14]malonyl-CoA incorporation, indicating that the first elongation cycle was targeted by acyl-ACP. All of the proteins required to catalyze the first round of fatty acid synthesis from acetyl-CoA plus malonyl-CoA in vivo were isolated, and the first fatty acid elongation cycle was reconstituted with these purified components. Analysis of the individual enzymes and the pattern of intermediate accumulation in the reconstituted system identified initiation of fatty acid synthesis by beta-ketoacyl-ACP synthase III (fabH) and enoyl-ACP reductase (fabI) in the elongation cycle as two steps attenuated by long chain acyl-ACP.