Plasma lipoproteins are carriers of various glycerophospholipids including diacyl, alkenyl/acyl, and alkyl/acyl glycerophosphocholines (GPCs), which become distributed among cells and tissues during metabolism. For metabolic function, these phospholipids require hydrolysis by phospholipases, but the responsible enzymes have not been identified. We had previously shown that after complete digestion of lipoprotein diacyl- and oxo-diacyl-GPCs, degradation of residual alkyl/acyl and alkenyl/acyl GPCs continues, despite the fact that ether lipids are resistant to hydrolysis by Ca²⁺-activated secretory PLA₂s and require the presence of the Ca²⁺-independent PLA₂. In the course of further investigation, we came across a report by Khaselev and Murphy in which the autoxidative degradation of plasmalogens in the presence of 2,2′-azobis(2-amidinopropane) dihydrochloride (AAPH) proceeded beyond the formation of dihydroperoxides, hydroxides and epoxides, and led to an attack on the enyl bond of the plasmalogen, resulting in formation of 1-OH/2-20:4-GPC and 1-formyl/2-20:4-GPC. Our preliminary investigation indicated that lipoprotein 16:0p/20:4ω6-GPC yielded the same autoxidation products as those reported for synthetic 16:0p/20:4ω6-GPC in the presence of AAPH. Such autoxidative degradation of lipoprotein plasmalogens had not been previously reported with or without AAPH. Subsequent study led to the conclusion that this reaction was not limited to arachidonates, but extended to other polyunsaturated eicosanoids, docosanoids, and tetracosanoids, as well as oligounsaturated octadecanoids. These observations led to a hypothesis that the autoxidative cleavage of the lipoprotein plasmalogens proceeded under the influence of apo-protein-derived free radicals as intermediates of oxidative processes.

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在与 V 组和 X 组分泌性磷脂酶 A2s 孵育期间破坏血浆脂蛋白的多不饱和烷基/酰基和烯基/酰基甘油磷酸胆碱

血浆脂蛋白是各种甘油磷脂的载体，包括二酰基、烯基/酰基和烷基/酰基甘油磷酸胆碱 (GPC)，它们在代谢过程中分布在细胞和组织中。对于代谢功能，这些磷脂需要被磷脂酶水解，但尚未确定负责的酶。我们之前已经表明，在脂蛋白二酰基-和氧代-二酰基-GPCs 完全消化后，残留的烷基/酰基和烯基/酰基 GPCs 的降解仍在继续，尽管醚脂对 Ca ²⁺活化的分泌 PLA的水解具有抗性₂ s 并且需要存在 Ca ²⁺独立的PLA ₂. 在进一步调查的过程中，我们遇到了 Khaselev 和 Murphy 的报告，其中缩醛磷脂在 2,2'-偶氮二（2-脒基丙烷）二盐酸盐 (AAPH) 存在下的自氧化降解超出了二氢过氧化物、氢氧化物的形成。和环氧化物，并导致对缩醛磷脂的烯键键的攻击，导致形成 1-OH/2-20:4-GPC 和 1-formyl/2-20:4-GPC。我们的初步调查表明，脂蛋白 16:0p/20:4ω6-GPC 在 AAPH 存在下产生与合成 16:0p/20:4ω6-GPC 相同的自氧化产物。这种脂蛋白缩醛磷脂的自氧化降解以前没有报道过伴有或不伴有 AAPH。随后的研究得出结论，该反应不仅限于花生四烯酸酯，还扩展到其他多不饱和类花生酸，二十二烷酸和二十四烷酸，以及寡不饱和十八烷酸。这些观察导致了一个假设，即脂蛋白缩醛磷脂的自氧化裂解是在作为氧化过程中间体的脱辅基蛋白衍生的自由基的影响下进行的。