Department of Plant Physiology, Adam Mickiewicz University, ul. Umultowska 89, 61-614 Poznań, Poland.
J Plant Physiol. 2011 Oct 15;168(15):1795-803. doi: 10.1016/j.jplph.2011.05.016. Epub 2011 Jul 12.
This study revealed that cytosolic aconitase (ACO, EC 4.2.1.3) and isocitrate lyase (ICL, EC 4.1.3.1, marker of the glyoxylate cycle) are active in germinating protein seeds of yellow lupine. The glyoxylate cycle seems to function not only in the storage tissues of food-storage organs, but also in embryonic tissue of growing embryo axes. Sucrose (60mM) added to the medium of in vitro culture of embryo axes and cotyledons decreased activity of lipase (LIP, EC 3.1.1.3) and activity of glutamate dehydrogenase (NADH-GDH, EC 1.4.1.2). The opposite effect was caused by sucrose on activity of cytosolic ACO, ICL as well as NADP(+)-dependent (EC 1.1.1.42) and NAD(+)-dependent (EC 1.1.1.41) isocitrate dehydrogenase (NADP-IDH and NAD-IDH, respectively); activity of these enzymes was clearly stimulated by sucrose. Changes in the activity of LIP, ACO, NADP-IDH, and NAD-IDH caused by sucrose were based on modifications in gene expression because corresponding changes in the enzyme activities and in the mRNA levels were observed. The significance of cytosolic ACO and NADP-IDH in carbon flow from storage lipid to amino acids, as well as the peculiar features of storage lipid breakdown during germination of lupine seeds are discussed.
本研究表明，细胞质中的顺乌头酸酶（ACO，EC 4.2.1.3）和异柠檬酸裂解酶（ICL，EC 4.1.3.1，乙醛酸循环的标志物）在黄羽扇豆发芽的蛋白质种子中活跃。乙醛酸循环似乎不仅在食物储存器官的储存组织中起作用，而且在生长胚胎轴的胚胎组织中也起作用。体外培养胚胎轴和子叶时，培养基中添加 60mM 的蔗糖会降低脂肪酶（LIP，EC 3.1.1.3）和谷氨酸脱氢酶（NADH-GDH，EC 1.4.1.2）的活性。蔗糖对细胞质 ACO、ICL 以及 NADP(+)-依赖性（EC 1.1.1.42）和 NAD(+)-依赖性（EC 1.1.1.41）异柠檬酸脱氢酶（NADP-IDH 和 NAD-IDH，分别）的活性有相反的影响；蔗糖明显刺激这些酶的活性。蔗糖引起的 LIP、ACO、NADP-IDH 和 NAD-IDH 活性的变化基于基因表达的修饰，因为观察到酶活性和 mRNA 水平的相应变化。细胞质 ACO 和 NADP-IDH 在从储存脂质到氨基酸的碳流中的重要性，以及羽扇豆种子发芽过程中储存脂质分解的特殊特征，都在本文中进行了讨论。
