Grant A J, Jessup W, Dean R T
Heart Research Institute, Camperdown, Sydney, Australia.
Free Radic Res Commun. 1993;19(2):125-34. doi: 10.3109/10715769309056507.
The location of a protein (soluble or membrane-bound) influences the extent of oxidative damage caused by free radicals. It has been established that after radical attack, soluble proteins can become more susceptible to hydrolysis by individual proteinases than native proteins. We have now examined the hydrolytic susceptibility following radical attack of a protein that is located within a membrane environment, mitochondrial monoamine oxidase (MAO). After exposure to oxygen radicals generated by gamma irradiation, hydrolysis of sub-mitochondrial particles (SMP) containing MAO was increased in three respects. First, the generation of small fragments of MAO by the proteinases elastase and trypsin, was enhanced. Second, the generation by these enzymes and by phospholipase A2 of non-sedimentable membrane fragments containing MAO was also increased. Third, autolysis of SMP was enhanced. Hence, proteins located within membranes may become more susceptible to enzymatic degradation following oxidative damage.
蛋白质（可溶性或膜结合型）的位置会影响自由基所造成的氧化损伤程度。已经确定，在自由基攻击后，可溶性蛋白质相比天然蛋白质会更易被个别蛋白酶水解。我们现在研究了位于膜环境中的一种蛋白质——线粒体单胺氧化酶（MAO）——在自由基攻击后的水解敏感性。在暴露于γ射线产生的氧自由基后，含有MAO的亚线粒体颗粒（SMP）的水解在三个方面有所增加。首先，蛋白酶弹性蛋白酶和胰蛋白酶对MAO小片段的生成增强。其次，这些酶以及磷脂酶A2对含有MAO的不可沉降膜片段的生成也增加。第三，SMP的自溶增强。因此，位于膜内的蛋白质在氧化损伤后可能会更易受到酶促降解。
