van der Donk E M, Vervaart J M, Verhagen J, Veldink G A, Vliegenthart J F
Bijvoet Center for Biomolecular Research, Department of Bio-Organic Chemistry, Utrecht University, Netherlands.
Biochim Biophys Acta. 1992 Sep 22;1128(1):14-25. doi: 10.1016/0005-2760(92)90252-q.
Rat basophilic leukemia cells exhibit 12-lipoxygenase activity only upon cell disruption. 12-Lipoxygenase may also possess 15-lipoxygenase activity, as is indicated by the formation of low amounts of 15(S)-HETE, in addition to the predominant product 12(S)-HETE, upon incubation of partially purified 12-lipoxygenase with arachidonic acid. With 5(S)-HPETE as substrate not only 5(S), 12(S)-diHETE and 5(S), 15(S)-diHETE are formed, but also LTA4, as was indicated by the presence of LTA4-derived LTB4-isomers. 12-Lipoxygenase from rat basophilic leukemia cells has many features in common with 12-lipoxygenase from bovine leukocytes. As was suggested for the latter enzyme, 12-lipoxygenase from rat basophilic leukemia cells may represent the remaining LTA4-synthase activity of 5-lipoxygenase, of which the 5-dioxygenase activity has disappeared upon cell disruption. Such a possible shift from 5-lipoxygenase activity to 12-lipoxygenase activity could not simply be induced by interaction of cytosolic 5-lipoxygenase with a membrane fraction after cell disruption, but may involve release of membrane-associated 5-lipoxygenase upon disruption of activated rat basophilic leukemia cells.
大鼠嗜碱性白血病细胞仅在细胞破裂时才表现出12-脂氧合酶活性。12-脂氧合酶可能还具有15-脂氧合酶活性，这可通过在将部分纯化的12-脂氧合酶与花生四烯酸一起孵育时，除了主要产物12(S)-HETE外，还形成少量15(S)-HETE来表明。以5(S)-HPETE作为底物时，不仅会形成5(S),12(S)-二羟二十碳四烯酸和5(S),15(S)-二羟二十碳四烯酸，还会形成白三烯A4（LTA4），这可通过LTA4衍生的白三烯B4（LTB4）异构体的存在来表明。大鼠嗜碱性白血病细胞中的12-脂氧合酶与牛白细胞中的12-脂氧合酶有许多共同特征。正如对后一种酶所提出的那样，大鼠嗜碱性白血病细胞中的12-脂氧合酶可能代表了5-脂氧合酶剩余的LTA4合酶活性，其中5-双加氧酶活性在细胞破裂后消失。从5-脂氧合酶活性到12-脂氧合酶活性的这种可能转变不能简单地通过细胞破裂后胞质5-脂氧合酶与膜部分的相互作用来诱导，而是可能涉及活化的大鼠嗜碱性白血病细胞破裂时膜相关5-脂氧合酶的释放。
