Tatulian S A, Steczko J, Minor W
Department of Molecular Physiology and Biological Physics, University of Virginia School of Medicine, Charlottesville 22906-0011, USA.
Biochemistry. 1998 Nov 3;37(44):15481-90. doi: 10.1021/bi981062t.
Lipoxygenases catalyze the biosynthesis of leukotrienes, lipoxins, and other lipid-derived mediators that are involved in a wide variety of pathophysiological processes, including inflammation, allergy, and tumorigenesis. Mammalian lipoxygenases are activated by a calcium-mediated translocation to intracellular membranes upon cell stimulation, and cooperate with cytosolic phospholipase A2 at the membrane surface to generate eicosanoids. Although it has been documented that plant cell stimulation increases intracellular Ca2+ concentration and activates cytosolic phospholipase A2, followed by lipoxygenase-catalyzed conversion of the liberated linolenic acid to jasmonic acid, no evidence is available for Ca2+-regulated membrane binding and activity of plant lipoxygenases. Plant lipoxygenases, unlike their mammalian counterparts, are believed to function independently of calcium or membranes. Here we present spectroscopic evidence for a calcium-regulated membrane-binding mechanism of soybean lipoxygenase-1 (L-1). Both calcium and membrane binding affect the structure and the mode of action of L-1. Free L-1 in solution is less accessible to the polar solvent and converts linoleic acid to conjugated dienes, whereas surface binding increases solvent accessibility and stimulates conjugated ketodiene production. Calcium exerts a biphasic effect on the structure and activity of L-1. Our results uncover a new regulatory mechanism for plant lipoxygenases and delineate common features in animal and plant cell signaling pathways.
脂氧合酶催化白三烯、脂oxin及其他脂质衍生介质的生物合成，这些介质参与多种病理生理过程，包括炎症、过敏和肿瘤发生。哺乳动物脂氧合酶在细胞受到刺激时通过钙介导的转位至细胞内膜而被激活，并在膜表面与胞质磷脂酶A2协同作用以生成类花生酸。尽管已有文献记载植物细胞受到刺激会增加细胞内Ca2+浓度并激活胞质磷脂酶A2，随后脂氧合酶催化将释放的亚麻酸转化为茉莉酸，但尚无证据表明植物脂氧合酶存在钙调节的膜结合及活性。与哺乳动物的脂氧合酶不同，植物脂氧合酶被认为其功能独立于钙或膜。在此，我们提供了大豆脂氧合酶-1（L-1）钙调节膜结合机制的光谱学证据。钙和膜结合均会影响L-1的结构和作用方式。溶液中的游离L-1较难被极性溶剂接近，并将亚油酸转化为共轭二烯，而表面结合则增加了溶剂可及性并刺激共轭酮二烯的产生。钙对L-1的结构和活性具有双相作用。我们的结果揭示了植物脂氧合酶的一种新的调节机制，并阐明了动物和植物细胞信号通路中的共同特征。
