Site-specific cross-linking of human and bovine hemoglobins differentially alters oxygen binding and redox side reactions producing rhombic heme and heme degradation.
Site-specific cross-linking of human and bovine hemoglobins differentially alters oxygen binding and redox side reactions producing rhombic heme and heme degradation.
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DOI：
10.1021/bi0121048
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发表时间：
2002-06
期刊：
影响因子：
2.9
通讯作者：
E. Nagababu;S. Ramasamy;J. Rifkind;Yiping Jia;A. Alayash
中科院分区：
文献类型：
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作者：
E. Nagababu;S. Ramasamy;J. Rifkind;Yiping Jia;A. Alayash
化学修饰的人或牛血红蛋白(Hb)已被开发为携氧疗法，目前正在进行临床评估。氧化过程在许多情况下会在引入降低氧亲和力的修饰时得到加强，这可能会限制这些蛋白质的安全性。我们对两种修饰的人血红蛋白(O-R-PolyHbA(0)和DBBF-Hb)和一种牛Hb(PolyHbBv)进行了系统的评价。我们都测量了HB制剂中存在的氧化产物，并跟踪了37摄氏度孵育期间的氧化反应。自氧化是引发氧化级联反应的主要氧化反应，与P(50)高度相关(R=0.987；p<；0.002)。然而，当比较其他氧化过程的结果时，发现了两种不同类别的氧化反应。与自氧化速率一样，所有修饰的HBS的氧铁Hb的形成都增加了。然而，随后的反应，导致血红素损伤和最终血红素降解，在修饰的人HBS中得到加强，但实际上在牛修饰的HBS中被抑制。通过电子顺磁共振测量的菱形血红素是对血红素造成不可逆损害的第一步，被发现是铁基Hb稳定性的可靠衡量标准，并有产生降解产物的趋势。DBBF-HB是一种基于Hb的氧气载体(HBOC)，其毒副作用已被很好地记录下来，具有最高水平的菱形血红素(比HBA(0)高41倍)，尽管其自氧化率相对较低。这些发现证实了在评估HBOCs的毒性时，这些次级氧化反应比自氧化反应更重要。
Chemically modified human or bovine hemoglobins (Hb) have been developed as oxygen-carrying therapeutics and are currently under clinical evaluation. Oxidative processes, which are in many cases enhanced when modifications are introduced that lower the oxygen affinity, can limit the safety of these proteins. We have carried out a systematic evaluation of two modified human Hbs (O-R-polyHbA(0) and DBBF-Hb) and one bovine Hb (polyHbBv). We have both measured the oxidative products present in the Hb preparations and followed the oxidative reactions during 37 degrees C incubations. Autoxidation, the primary oxidative reaction which initiates the oxidative cascade, is highly correlated with P(50) (R = 0.987; p < 0.002). However, when the results for the other oxidative processes are compared, two different classes of oxidative reactions are identified. The formation of oxyferrylHb, like the rate of autoxidation, increases for all modified Hbs. However, the subsequent reactions, which lead to heme damage and eventually heme degradation, are enhanced for the modified human Hbs but are actually suppressed for bovine-modified Hbs. The rhombic heme measured by electron paramagnetic resonance, which is the initial step that causes irreversible damage to the heme, is found to be a reliable measure of the stability of ferrylHb and has the tendency to produce degradation products. DBBF-Hb, a Hb-based oxygen carrier (HBOC) for which toxic side effects have been well documented, has the highest level of rhombic heme (41-fold greater than for HbA(0)), even though its rate of autoxidation is relatively low. These findings establish the importance of these secondary oxidative reactions over autoxidation in evaluating the toxicity of HBOCs.