Incorporation of newly synthesized fatty acids into cytosolic glycerolipids in pea leaves occurs via acyl editing
Incorporation of newly synthesized fatty acids into cytosolic glycerolipids in pea leaves occurs via acyl editing
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DOI：
10.1074/jbc.m705447200
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发表时间：
2007-10-26
影响因子：
4.8
通讯作者：
Pollard, Mike
中科院分区：
文献类型：
--
作者：
Bates, Philip D.;Ohlrogge, John B.;Pollard, Mike
在扩展豌豆叶，超过95%的脂肪酸（FA）合成的质体出口的真核甘油脂的装配。通常认为，质体FA合成的主要产物（18：1和16：0）首先掺入磷脂酸（PA）的16：0/18：1和18：1/18：1分子种类，然后转化为磷脂酰胆碱（PC），主要的真核磷脂和酰基去饱和位点。然而，通过用[C-14]乙酸酯、[C-14]甘油和[C-14]二氧化碳标记豌豆叶的脂质，我们证明酰基编辑是真核生物甘油脂质合成的一个组成部分。首先，在非常早的时间点没有观察到PA和PC [C-14]酰基链之间的底物-产物关系。其次，在这些早期时间点对PC分子种类的分析显示，> 90%的新合成的[C-14] 18：1和[C-14] 16：0酰基与先前合成的未标记酰基（18：2、18：3或16：0）一起并入PC中。第三，[C-14]甘油标记产生了高度富集18：2、18：3和16：0 FA的PC分子种类，而不是质体脂肪酸合成的主要产物18：1。总之，我们提出，大多数新合成的酰基不会立即用于PA合成，而是通过在sn-1和sn-2位置操作的酰基编辑机制直接并入PC。此外，通过酰基编辑去除的酰基主要用于通过甘油3-磷酸酰化的PC的净合成。
In expanding pea leaves, over 95% of fatty acids (FA) synthesized in the plastid are exported for assembly of eukaryotic glycerolipids. It is often assumed that the major products of plastid FA synthesis (18:1 and 16:0) are first incorporated into 16:0/18:1 and 18:1/18:1 molecular species of phosphatidic acid (PA), which are then converted to phosphatidylcholine (PC), the major eukaryotic phospholipid and site of acyl desaturation. However, by labeling lipids of pea leaves with [C-14] acetate, [C-14] glycerol, and [C-14] carbon dioxide, we demonstrate that acyl editing is an integral component of eukaryotic glycerolipid synthesis. First, no precursor-product relationship between PA and PC [C-14] acyl chains was observed at very early time points. Second, analysis of PC molecular species at these early time points showed that > 90% of newly synthesized [C-14] 18:1 and [C-14] 16:0 acyl groups were incorporated into PC alongside a previously synthesized unlabeled acyl group (18:2, 18:3, or 16:0). And third, [C-14] glycerol labeling produced PC molecular species highly enriched with 18:2, 18:3, and 16:0 FA, and not 18:1, the major product of plastid fatty acid synthesis. In conclusion, we propose that most newly synthesized acyl groups are not immediately utilized for PA synthesis, but instead are incorporated directly into PC through an acyl editing mechanism that operates at both sn-1 and sn-2 positions. Additionally, the acyl groups removed by acyl editing are largely used for the net synthesis of PC through glycerol 3-phosphate acylation.