Fulda Martin, Shockey Jay, Werber Martin, Wolter Frank P, Heinz Ernst
Universität Hamburg, Institut für Allgemeine Botanik, Ohnhorststr. 18, 22609 Hamburg, Germany. fulda.wsu.edu
Plant J. 2002 Oct;32(1):93-103. doi: 10.1046/j.1365-313x.2002.01405.x.
Post-germinative growth of oilseeds is dependent on the breakdown of the stored lipid reserves. Long-chain acyl-CoA synthetase activities (LACS) are critically involved in this process by activating the released free fatty acids and thus feeding the beta-oxidation cycle in glyoxysomes. Here we report on the identification of two LACS genes, AtLACS6 and AtLACS7 from Arabidopsis thaliana coding for peroxisomal LACS proteins. The subcellular localization was verified by co-expression studies of spectral variants of the green fluorescent protein (GFP). While AtLACS6 is targeted by a type 2 (PTS2) peroxisomal targeting sequence, for AtLACS7 a functional PTS1 as well as a PTS2 could be demonstrated. Possible explanations for this potentially redundant targeting information will be discussed. Expression studies of both genes revealed a strong induction 1 day after germination resembling the expression pattern of other genes involved in beta-oxidation. Analysis of the substrate specificities of the two LACS proteins demonstrated enzymatic activity for both enzymes with the whole spectrum of fatty acids found in stored lipid reserves. These results suggest that both LACS proteins might have overlapping functions and are able to initiate beta-oxidation in plant peroxisomes.
油料种子萌发后的生长依赖于储存脂质储备的分解。长链酰基辅酶A合成酶活性（LACS）通过激活释放的游离脂肪酸并进而为乙醛酸循环体中的β-氧化循环提供底物，在这一过程中起着关键作用。在此，我们报道了从拟南芥中鉴定出两个LACS基因，AtLACS6和AtLACS7，它们编码过氧化物酶体LACS蛋白。通过绿色荧光蛋白（GFP）光谱变体的共表达研究验证了亚细胞定位。AtLACS6由2型（PTS2）过氧化物酶体靶向序列靶向，而对于AtLACS7，可证明其具有功能性PTS1以及PTS2。将讨论这种潜在冗余靶向信息的可能解释。对这两个基因的表达研究表明，萌发后1天有强烈诱导，类似于参与β-氧化的其他基因的表达模式。对两种LACS蛋白底物特异性的分析表明，两种酶对储存脂质储备中发现的全谱脂肪酸均具有酶活性。这些结果表明，两种LACS蛋白可能具有重叠功能，并能够在植物过氧化物酶体中启动β-氧化。
