Peroxidase activity of hemoglobin towards ascorbate and urate: A synergistic protective strategy against toxicity of Hemoglobin-Based Oxygen Carriers (HBOC)
Peroxidase activity of hemoglobin towards ascorbate and urate: A synergistic protective strategy against toxicity of Hemoglobin-Based Oxygen Carriers (HBOC)
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DOI：
10.1016/j.bbapap.2008.03.019
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发表时间：
2008-10-01
影响因子：
3.2
通讯作者：
Buehler, Paul W.
中科院分区：
文献类型：
--
作者：
Cooper, Chris E.;Silaghi-Dumitrescu, Radu;Buehler, Paul W.
作为具有体积膨胀性质的氧桥连剂（“血液替代品”）开发的无细胞血红蛋白易于在循环中发生自氧化和氧化剂介导的结构变化。在过氧化氢和抗坏血酸或尿酸盐的存在下，我们表明，铁血红蛋白的功能作为一个真正的酶过氧化物酶。两种底物的活性均饱和，并与蛋白质浓度呈线性相关。活性在低pH下增强，pK（a）为4.7，与作为活性中间体的铁基物质（Fe（IV）-OH）的质子化一致。为了测试这些氧化还原反应是否定义了其在体内的行为，我们用50%聚合牛血红蛋白（PolyHbBv）交换了输注的豚鼠，并监测了内源性抗坏血酸盐和尿酸盐的血浆水平。输血后立即，Met PolyHbBv水平增加至总Hb的30%，并在输血后的前24小时内保持在该水平。输血后血浆抗坏血酸降低了50%，而尿酸水平保持不变。一个简单的动力学模型，假设抗坏血酸是一个更活跃的铁血红素还原酶和过氧化物酶底物比尿酸盐，与体内数据是一致的。本研究结果证实了抗坏血酸盐和尿酸盐分别在维持输注Hb的氧化稳定性中的主要和次要作用。(c)2008 Elsevier B. V.保留所有权利。
Acellular hemoglobins developed as oxygen bridging agents with volume expanding properties ("blood substitutes") are prone to autoxidation and oxidant-mediated structural changes in circulation. In the presence of hydrogen peroxide and either ascorbate or urate we show that ferric hemoglobin functions as a true enzymatic peroxidase. The activity saturates with both substrates and is linearly dependent on protein concentration. The activity is enhanced at low pH with a pK(a) of 4.7, consistent with protonation of the ferryl species (Fe(IV)-OH) as the active intermediate. To test whether these redox reactions define its behaviour in vivo we exchanged transfused guinea pigs with 50% polymerized bovine Hb (PolyHbBv) and monitored plasma levels of endogenous ascorbate and urate. immediately after transfusion, met PolyHbBv levels increased up to 30% of total Hb and remained at this level during the first 24 h post transfusion. Plasma ascorbate decreased by 50% whereas urate levels remained unchanged after transfusion. A simple kinetic model, assuming that ascorbate was a more active ferric heme reductase and peroxidase substrate than urate, was consistent with the in vivo data. The present finding confirms the primary and secondary roles of ascorbate and urate respectively in maintaining the oxidative stability of infused Hb. (c) 2008 Elsevier B.V. All rights reserved.