Meucci E, Mordente A, Martorana G E
Istituto di Chimica Biologica, Università Cattolica del S. Curore, Facoltà di Medicina e Chirurgia, Roma, Italy.
J Biol Chem. 1991 Mar 15;266(8):4692-9.
Mild oxidative stress, as elicited by ascorbate, oxygen, and trace metals, affects the binding properties of human serum albumin via purely conformational changes. In fact, no gross alteration can be observed in the electrophoretic and chromatographic patterns of albumin, whereas localized modifications are indicated by the changes in absorption and fluorescence spectra and in polarization degree. The oxidized protein presents a small increase of bityrosine production and a time-dependent increase in the content of carbonyl groups, whereas proteolytic susceptibility is unchanged. A higher affinity for cis-parinaric acid and a slight loss of solubility in high salt indicate a greater surface hydrophobicity. Pinpoint denaturation of the albumin molecule is also suggested by a decreased "esterase" activity in the presence of p-nitrophenyl acetate. Conformational stability evaluated through thermal shock and addition of moderate amounts of guanidine indicate that the oxidized protein is more heat-resistant, less flexible, and more rigid than the native one. Although limited, structural damages afforded by the oxidative stress cause alterations of albumin binding properties as documented by experiments with probes and physiological ligands. The loss of biological activity of human serum albumin induced by ascorbate system appears of medical relevance, because it can affect drug metabolism and particularly drug tolerance in the elderly.
由抗坏血酸盐、氧气和痕量金属引发的轻度氧化应激，通过纯粹的构象变化影响人血清白蛋白的结合特性。事实上，在白蛋白的电泳和色谱图谱中未观察到明显变化，而吸收光谱、荧光光谱及偏振度的改变表明存在局部修饰。氧化后的蛋白质双酪氨酸生成量略有增加，羰基含量随时间增加，而蛋白水解敏感性未变。对顺式十八碳四烯酸的亲和力更高，在高盐环境中的溶解度略有降低，表明表面疏水性增强。在对硝基苯乙酸存在下“酯酶”活性降低也表明白蛋白分子存在定点变性。通过热休克和添加适量胍评估的构象稳定性表明，氧化后的蛋白质比天然蛋白质更耐热、柔韧性更差且更刚性。尽管氧化应激造成的结构损伤有限，但如用探针和生理配体进行的实验所证明的，它会导致白蛋白结合特性改变。抗坏血酸盐系统诱导的人血清白蛋白生物活性丧失似乎具有医学相关性，因为它会影响药物代谢，尤其是老年人的药物耐受性。
