Edenius C, Heidvall K, Lindgren J A
Department of Physiological Chemistry, Karolinska Institutet, Stockholm, Sweden.
Eur J Biochem. 1988 Dec 1;178(1):81-6. doi: 10.1111/j.1432-1033.1988.tb14431.x.
Human platelets dose-dependently converted exogenous leukotriene A4 to leukotriene C4 and efficiently metabolized this compound to leukotrienes D4 and E4. Neither of these compounds were produced after stimulation of human platelet suspensions with ionophore A23187. After LTA4 incubation of subcellular fractions, formation of leukotriene C4 was exclusively observed in the particulate fraction and was separable from the classical glutathione S-transferase activity. This suggested the presence of a specific leukotriene C4 synthase in human platelets. Addition of physiological amounts of autologous platelets to human granulocyte suspensions significantly increased ionophore A23187-induced formation of leukotriene C4. In contrast, the production of leukotriene B4 was decreased. After preincubation of platelets with [35S]cysteine, 35S-labeled leukotriene C4 was produced by A23187-stimulated platelet-granulocyte suspensions, strongly indicating a transcellular biosynthesis of this compound.
人血小板可将外源性白三烯A4剂量依赖性地转化为白三烯C4，并能有效地将该化合物代谢为白三烯D4和E4。在用离子载体A23187刺激人血小板悬液后，未产生这些化合物中的任何一种。在亚细胞组分与白三烯A4孵育后，仅在微粒体组分中观察到白三烯C4的形成，并且它与经典的谷胱甘肽S-转移酶活性可分离。这表明人血小板中存在一种特异性白三烯C4合成酶。向人粒细胞悬液中添加生理量的自体血小板可显著增加离子载体A23187诱导的白三烯C4的形成。相反，白三烯B4的产生减少。在用[35S]半胱氨酸预孵育血小板后，A23187刺激的血小板-粒细胞悬液产生了35S标记的白三烯C4，强烈表明该化合物的跨细胞生物合成。
