Hagmann W, Kagawa D, Renaud C, Honn K V
Dept. of Radiation Oncology, Wayne State University, Detroit, MI 48202.
Prostaglandins. 1993 Dec;46(6):471-7. doi: 10.1016/0090-6980(93)90066-g.
The understanding of the intracellular regulation of 12-lipoxygenase requires a knowledge of the distribution of both enzyme protein and its activity. In human erythroleukemia cells, the membrane fraction contains about 90% of the total cellular 12-lipoxygenase activity, whereas only approximately 10% of 12-lipoxygenase activity resides in the cytosol. However, the majority of the cellular 12-lipoxygenase protein is found in the cytosol. Pretreatment of cells for 0-3 days with 160 nM TPA caused a marked, time-dependent increase in membrane-bound 12-lipoxygenase activity and protein, respectively. In contrast, the cytosolic amount of 12-lipoxygenase protein and activity, respectively, were minimally altered by this TPA treatment. Recombining the active membrane fraction with cytosol resulted in no significant inhibition of its 12-lipoxygenase activity, but the addition of GSH to the membrane fraction inhibited 12-lipoxygenase activity in a dose-dependent manner. On the other hand, the cytosolic enzyme can be rendered active in the presence of 1 microM 13-hydroperoxyoctadecadienoic acid. In HEL cell homogenates, a partial translocation of the cytosolic enzyme to the membrane takes place in a Ca(2+)-dependent manner, resulting in an increase in membrane-associated 12-lipoxygenase activity and a concomitant decrease in cytosolic 12-lipoxygenase activity above 0.1 microM Ca2+.
要了解12 - 脂氧合酶的细胞内调节，需要知晓该酶蛋白的分布及其活性。在人红白血病细胞中，膜组分含有约90%的细胞总12 - 脂氧合酶活性，而只有约10%的12 - 脂氧合酶活性存在于胞质溶胶中。然而，细胞中的大部分12 - 脂氧合酶蛋白存在于胞质溶胶中。用160 nM佛波酯（TPA）对细胞预处理0 - 3天，分别导致膜结合的12 - 脂氧合酶活性和蛋白显著且呈时间依赖性增加。相比之下，这种TPA处理对胞质溶胶中12 - 脂氧合酶蛋白量和活性的改变极小。将有活性的膜组分与胞质溶胶重新组合，并未导致其12 - 脂氧合酶活性受到显著抑制，但向膜组分中添加谷胱甘肽（GSH）会以剂量依赖性方式抑制12 - 脂氧合酶活性。另一方面，在存在1 microM 13 - 氢过氧十八碳二烯酸的情况下，胞质溶胶中的酶可被激活。在人红白血病（HEL）细胞匀浆中，胞质溶胶中的酶会以钙离子（Ca(2+)）依赖的方式部分转运至膜上，导致膜相关的12 - 脂氧合酶活性增加，同时在钙离子浓度高于0.1 microM时，胞质溶胶中12 - 脂氧合酶活性相应降低。
