Code Christian, Mahalka Ajay K, Bry Kristian, Kinnunen Paavo K J
Helsinki Biophysics and Biomembrane Group, Medical Biochemistry, Institute of Biomedicine, University of Helsinki, Finland.
Biochim Biophys Acta. 2010 Aug;1798(8):1593-600. doi: 10.1016/j.bbamem.2010.05.002. Epub 2010 May 10.
Oxidative stress leads to drastic modifications of both the biophysical properties of biomembranes and their associated chemistry imparted upon the formation of oxidatively modified lipids. To this end, oxidized phospholipid derivatives bearing an aldehyde function, such as 1-palmitoyl-2-(9'-oxo-nonanoyl)-sn-glycero-3-phosphocholine (PoxnoPC) can covalently react with proteins that come into direct contact. Intriguingly, we observed PoxnoPC in a 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) matrix to shorten and abolish the lag time in the action of phospholipase A2 (PLA2) on this composite substrate, with concomitant augmented decrement in pH, indicating more extensive hydrolysis, which was in keeping with enhanced 90 degrees light scattering. The latter was abolished by the aldehyde scavenger methoxyamine, thus suggesting the involvement of Schiff base. Enhanced hydrolysis of a fluorescent phospholipid analogue was seen for PLA2 preincubated with PoxnoPC. Mixing PLA2 with submicellar (22 microM) PoxnoPC caused a pronounced increase in Thioflavin T fluorescence, in keeping with the formation of amyloid-type fibers, which were seen also by electron microscopy.
氧化应激会导致生物膜的生物物理特性及其相关化学性质发生剧烈改变，这些改变是由氧化修饰脂质的形成所引起的。为此，带有醛基功能的氧化磷脂衍生物，如1-棕榈酰-2-(9'-氧代壬酰基)-sn-甘油-3-磷酸胆碱（PoxnoPC），可以与直接接触的蛋白质发生共价反应。有趣的是，我们观察到在1,2-二棕榈酰-sn-甘油-3-磷酸胆碱（DPPC）基质中的PoxnoPC能够缩短并消除磷脂酶A2（PLA2）作用于这种复合底物时的延迟时间，同时伴随着pH值的进一步降低，这表明水解作用更广泛，这与增强的90度光散射一致。后者可被醛清除剂甲氧基胺消除，因此表明席夫碱参与其中。对于与PoxnoPC预孵育的PLA2，观察到荧光磷脂类似物的水解增强。将PLA2与亚胶束（22 microM）的PoxnoPC混合会导致硫黄素T荧光显著增加，这与淀粉样纤维的形成一致，电子显微镜也观察到了这些纤维。
