Sugiura T, Ojima-Uchiyama A, Masuzawa Y, Fujita M, Nakagawa Y, Waku K
Faculty of Pharmaceutical Sciences, Teikyo University, Kanagawa, Japan.
Lipids. 1991 Dec;26(12):974-8. doi: 10.1007/BF02536487.
Activities of enzymes which metabolize lysoplatelet-activating factor (lysoPAF) and platelet-activating factor (PAF) were studied in rabbit alveolar macrophage lysates. Substantial acetyltransferase activity was noted in the presence of 100 microM acetyl-coenzyme A (CoA), and this activity was increased in A23187-stimulated cell lysate. On the other hand, in the absence of exogenous acetyl-CoA, lysoPAF was mainly acylated through a transacylation pathway rather than by acetyltransferase in both control and A23187-stimulated cell lysates. We confirmed that the intracellular concentration of acetyl-CoA is relatively low. The observations suggest that the transacylation system may play an equally important role in the regulation of the availability of lysoPAF in intact cells. Intracellular lysoPAF was also maintained at relatively low levels. Interestingly, large amounts of PAF were produced even in unstimulated cells upon addition of an excess of exogenous lysoPAF, suggesting that generation of an adequate amount of lysoPAF within cells may be sufficient to trigger PAF synthesis in this type of cells.
在兔肺泡巨噬细胞裂解物中研究了代谢溶血血小板活化因子（lysoPAF）和血小板活化因子（PAF）的酶的活性。在存在100微摩尔乙酰辅酶A（CoA）的情况下，观察到大量的乙酰转移酶活性，并且在A23187刺激的细胞裂解物中该活性增加。另一方面，在没有外源性乙酰辅酶A的情况下，在对照和A23187刺激的细胞裂解物中，lysoPAF主要通过转酰基途径而非乙酰转移酶进行酰化。我们证实细胞内乙酰辅酶A的浓度相对较低。这些观察结果表明，转酰基系统在完整细胞中lysoPAF可用性的调节中可能起着同样重要的作用。细胞内lysoPAF也维持在相对较低的水平。有趣的是，即使在未刺激的细胞中，加入过量的外源性lysoPAF后也会产生大量的PAF，这表明在细胞内产生足够量的lysoPAF可能足以触发这类细胞中PAF的合成。
