由拟南芥中的五个基因编码的九种3-酮酰基-CoA硫磺酶（KAT）和乙酰乙酰基-CoA硫酶（ACAT）被靶向过氧化物酶体或胞质溶胶，但不靶向线粒体。,Plant Molecular Biology

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由拟南芥中的五个基因编码的九种3-酮酰基-CoA硫磺酶（KAT）和乙酰乙酰基-CoA硫酶（ACAT）被靶向过氧化物酶体或胞质溶胶，但不靶向线粒体。
Plant Molecular Biology ( IF 3.9 ) Pub Date : 2006-11-23 , DOI: 10.1007/s11103-006-9075-1
Chris Carrie ₁ , Monika W Murcha , A Harvey Millar , Steven M Smith , James Whelan

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脂肪酸β-氧化酶在植物中的亚细胞定位是有争议的。在当前的辩论中，特定硫醇在脂肪酸降解，脂肪酸合成和异亮氨酸降解中的作用和位置很重要。这项研究的目的是确定亚细胞的位置，并因此提供有关拟南芥中所有假定的3-酮酰基-CoA硫代酶（KAT）和乙酰乙酰-CoA硫代酶（ACAT）可能功能的信息。拟南芥具有三个预计编码KAT的基因，其中一个编码两个在N末端不同的多肽。在拟南芥属细胞中表达的cDNA编码在C末端与绿色荧光蛋白（GFP）融合的这些KAT的每一个，表明三个靶向过氧化物酶体，而第四个显然是胞质。还预测这四个KAT具有线粒体靶向序列，但纯化的线粒体无法在体外导入任何蛋白质。拟南芥还具有两个编码总共五个不同推定ACAT的基因。一种同工型以与GFP融合的方式靶向过氧化物酶体，而另一种同工型则没有以GFP融合体的形式靶向体内，或导入分离的线粒体中。对拟南芥中基因共表达簇的分析表明，过氧化物酶体KAT2在β-氧化中起作用，而KAT5与类黄酮生物合成途径的基因共表达，而胞质ACAT2显然与胞质甲羟戊酸生物合成途径的基因共表达。我们得出的结论是，KAT和ACAT存在于细胞质和过氧化物酶体中，但在线粒体中却没有。

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Nine 3-ketoacyl-CoA thiolases (KATs) and acetoacetyl-CoA thiolases (ACATs) encoded by five genes in Arabidopsis thaliana are targeted either to peroxisomes or cytosol but not to mitochondria.

The sub-cellular location of enzymes of fatty acid beta-oxidation in plants is controversial. In the current debate the role and location of particular thiolases in fatty acid degradation, fatty acid synthesis and isoleucine degradation are important. The aim of this research was to determine the sub-cellular location and hence provide information about possible functions of all the putative 3-ketoacyl-CoA thiolases (KAT) and acetoacetyl-CoA thiolases (ACAT) in Arabidopsis. Arabidopsis has three genes predicted to encode KATs, one of which encodes two polypeptides that differ at the N-terminal end. Expression in Arabidopsis cells of cDNAs encoding each of these KATs fused to green fluorescent protein (GFP) at their C-termini showed that three are targeted to peroxisomes while the fourth is apparently cytosolic. The four KATs are also predicted to have mitochondrial targeting sequences, but purified mitochondria were unable to import any of the proteins in vitro. Arabidopsis also has two genes encoding a total of five different putative ACATs. One isoform is targeted to peroxisomes as a fusion with GFP, while the others display no targeting in vivo as GFP fusions, or import into isolated mitochondria. Analysis of gene co-expression clusters in Arabidopsis suggests a role for peroxisomal KAT2 in beta-oxidation, while KAT5 co-expresses with genes of the flavonoid biosynthesis pathway and cytosolic ACAT2 clearly co-expresses with genes of the cytosolic mevalonate biosynthesis pathway. We conclude that KATs and ACATs are present in the cytosol and peroxisome, but are not found in mitochondria. The implications for fatty acid beta-oxidation and for isoleucine degradation in mitochondria are discussed.

更新日期：2019-11-01

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