Laboratoire de Physiologie Cellulaire, Université Pierre et Marie Curie, 4, place Jussieu, Tour 53 3E, 75252 Paris Cedex 05, France.
Plant Physiol. 1992 Sep;100(1):472-81. doi: 10.1104/pp.100.1.472.
When incubated with [1-(14)C]acetate and cofactors (ATP, Coenzyme A, sn-glycerol-3-phosphate, UDPgalactose, and NADH), intact chloroplasts synthesized fatty acids that were subsequently incorporated into most of the lipid classes. To study lipid synthesis at the chloroplast envelope membrane level, (14)C-labeled pea (Pisum sativum) chloroplasts were subfractionated using a single flotation gradient. The different envelope membrane fractions were characterized by their density, lipid and polypeptide composition, and the localization of enzymic activities (UDPgalactose-1,2 diacylglycerol galactosyltransferase, Mg(2+)-dependent ATPase). They were identified as very pure outer membranes (light fraction) and strongly enriched inner membranes (heavy fraction). A fraction of intermediate density, which probably contained double membranes, was also isolated. Labeled glycerolipids recovered in the inner envelope membrane were phosphatidic acid, phosphatidyl-glycerol, 1,2 diacylglycerol, and monogalactosyldiacylglycerol. Their (14)C-fatty acid composition indicated that a biosynthetic pathway similar to the prokaryotic pathway present in cyanobacteria occurred in the inner membrane. In the outer membrane, phosphatidylcholine was the most labeled glycerolipid. Phosphatidic acid, phosphatidylglycerol, 1,2 diacylglycerol, and monogalactosyldiacylglycerol were also labeled. The (14)C-fatty acid composition of these lipids showed a higher proportion of oleate than palmitate. This labeling, different from that of the inner membrane, could result either from transacylation activities or from a biosynthetic pathway not yet described in pea and occurring partly in the outer chloroplast envelope membrane. This metabolism would work on an oleate-rich pool of fatty acids, possibly due to the export of oleate from chloroplast toward the extrachloroplastic medium. The respective roles of each membrane for chloroplast lipid synthesis are emphasized.
当与 [1-(14)C] 乙酸和辅助因子（ATP、辅酶 A、sn-甘油-3-磷酸、UDP 半乳糖和 NADH）一起孵育时，完整的叶绿体合成了随后被纳入大多数脂质类别的脂肪酸。为了在叶绿体包膜水平上研究脂质合成，使用单一浮选梯度对（14)C 标记的豌豆（Pisum sativum）叶绿体进行亚分级。不同的包膜膜部分通过其密度、脂质和多肽组成以及酶活性（UDP 半乳糖-1,2 二酰基甘油半乳糖基转移酶、Mg(2+)-依赖性 ATP 酶）的定位来表征。它们被鉴定为非常纯净的外膜（轻级分）和强烈富集的内膜（重级分）。还分离出了一种中间密度的部分，可能含有双层膜。在内膜中回收的标记甘油磷脂是磷脂酸、磷脂酰甘油、1,2 二酰基甘油和单半乳糖基二酰基甘油。它们的（14)C-脂肪酸组成表明，在内膜中存在类似于蓝细菌中的原核途径的生物合成途径。在外膜中，磷脂酰胆碱是标记甘油磷脂中含量最多的。磷脂酸、磷脂酰甘油、1,2 二酰基甘油和单半乳糖基二酰基甘油也被标记。这些脂质的（14)C-脂肪酸组成显示出油酸的比例高于棕榈酸。这种标记与内膜的标记不同，可能是由于外膜中的转酰基酶活性或豌豆中尚未描述的生物合成途径引起的，该途径部分发生在外膜叶绿体中。这种代谢将在富含油酸的脂肪酸库上进行，可能是由于油酸从叶绿体向质外体介质的输出。强调了每个膜在叶绿体脂质合成中的各自作用。
