Molecular characterization of a heteromeric ATP-citrate lyase that generates cytosolic acetyl-coenzyme A in Arabidopsis
Molecular characterization of a heteromeric ATP-citrate lyase that generates cytosolic acetyl-coenzyme A in Arabidopsis
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DOI：
10.1104/pp.008110
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发表时间：
2002-10-01
期刊：
影响因子：
7.4
通讯作者：
Wurtele, ES
中科院分区：
文献类型：
--
作者：
Fatland, BL;Ke, JS;Wurtele, ES
乙酰辅酶A（CoA）在植物细胞的胞质溶胶中用于合成多种植物化学物质，包括蜡、类异戊二烯、芪和类黄酮。胞浆乙酰辅酶A的来源尚不清楚。我们确定了两个拟南芥cDNA编码的蛋白质类似于人类ATP-柠檬酸裂解酶（ACL）的氨基和羧基部分。这些cDNA在酵母（酿酒酵母）中的共表达赋予ACL活性，表明这两个拟南芥基因是ACL活性所必需的。拟南芥ACL是由两个不同的亚基ACLA（45 kD）和ACLB（65 kD）组成的异聚体酶。全蛋白的分子量为500 kD，对应于具有A（4）B（4）构型的杂八聚体。ACL活性以及ACLA和ACLB多肽位于胞质溶胶中，这与ACLA和ACLB序列中缺乏靶向肽一致。在拟南芥基因组中，三个基因编码ACLA亚基（ACLA-1，At 1g 10670; ACLA-2，At 1g 60810;和ACLA-3，At 1g 09430），两个基因编码ACLB亚基（ACLB-1，At 3g 06650和ACLB-2，At 5g 49460）。ACLA和ACLB mRNA在植物发育过程中以协调的时空模式积累。这种复杂的积累模式与胞质乙酰辅酶A的预测生理需求一致，并且与胞质乙酰辅酶A羧化酶（一种使用胞质乙酰辅酶A作为底物的酶）的积累模式密切协调。总而言之，这些结果表明，由拟南芥ACLA和ACLB基因编码的ACL会产生细胞质乙酰辅酶A。这种酶的异聚体结构在绿色植物（包括绿藻纲、地钱纲、苔藓纲、松科、单子叶植物和真双子叶植物）、真菌、蓝绿藻、衣原体和原核生物中是常见的。与此相反，所有已知的动物ACL酶都具有同源结构，这表明ACLA和ACLB基因的进化融合可能发生在这个王国的进化历史早期。
Acetyl-coenzyme A (CoA) is used in the cytosol of plant cells for the synthesis of a diverse set of phytochemicals including waxes, isoprenoids, stilbenes, and flavonoids. The source of cytosolic acetyl-CoA is unclear. We identified two Arabidopsis cDNAs that encode proteins similar to the amino and carboxy portions of human ATP-citrate lyase (ACL). Coexpression of these cDNAs in yeast (Saccharomyces cerevisiae) confers ACL activity, indicating that both the Arabidopsis genes are required for ACL activity. Arabidopsis ACL is a heteromeric enzyme composed of two distinct subunits, ACLA (45 kD) and ACLB (65 kD). The holoprotein has a molecular mass of 500 kD, which corresponds to a heterooctomer with an A(4)B(4) configuration. ACL activity and the ACLA and ACLB polypeptides are located in the cytosol, consistent with the lack of targeting peptides in the ACLA and ACLB sequences. In the Arabidopsis genome, three genes encode for the ACLA subunit (ACLA-1, At1g10670; ACLA-2, At1g60810; and ACLA-3, At1g09430), and two genes encode the ACLB subunit (ACLB-1, At3g06650 and ACLB-2, At5g49460). The ACLA and ACLB mRNAs accumulate in coordinated spatial and temporal patterns during plant development. This complex accumulation pattern is consistent with the predicted physiological needs for cytosolic acetyl-CoA, and is closely coordinated with the accumulation pattern of cytosolic acetyl-CoA carboxylase, an enzyme using cytosolic acetyl-CoA as a substrate. Taken together, these results indicate that ACL, encoded by the ACLA and ACLB genes of Arabidopsis, generates cytosolic acetyl-CoA. The heteromeric organization of this enzyme is common to green plants (including Chlorophyceae, Marchantimorpha, Bryopsida, Pinaceae, monocotyledons, and eudicots), species of fungi, Glaucophytes, Chlamydomonas, and prokaryotes. In contrast, all known animal ACL enzymes have a homomeric structure, indicating that a evolutionary fusion of the ACLA and ACLB genes probably occurred early in the evolutionary history of this kingdom.