血红素化学中的电子迁移反应:以亚氯酸盐歧化酶为例
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- 英文论文题名：Electron Transfer in Heme Chemistry:The Case of Chlorite Dismutase
- 论文作者：苏璟璇 ; 陈世稆
- 英文论文作者：Jing-Xuan Su ; Shi-Lu Chen ; Key Laboratory of Cluster Science of Ministry of Education ; Beijing Key Laboratory of Photoelectronic/Electrophotonic Conversion Materials ; School of Chemistry ; Beijing Institute of Technology
- 年：2016
- 作者机构：北京理工大学化学学院原子分子簇科学教育部重点实验室,光电转换材料理论与技术重点实验室;
- 论文关键词：亚氯酸盐歧化酶 ; 密度泛函计算 ; 电子迁移 ; 血红素蛋白质 ; 过氧乙酸
- 会议召开时间：2016-07-01
- 会议录名称：中国化学会第30届学术年会摘要集-第十九分会：化学中的量子与经典动力学
- 语种：中文
- 分类号：O641.1
- 学会代码：ZGHY
- 会议名称：中国化学会第30届学术年会-第十九分会 ; 化学中的量子与经典动力学
- 会议地点：中国辽宁大连
- 主办单位：中国化学会
- 学会名称：中国化学会
- 页数：1
- 文件大小：239k
- 原文格式：D
- 会议级别：全国
摘要
在血红素化学中,电子迁移(ET)现象是非常重要的,但通常它却很难被实验技术手段表征。我们运用密度泛函理论(DFT)计算,优化得到了亚氯酸盐歧化酶(Cld)催化分解过氧乙酸(PAA)时的电子迁移的过渡态。计算表明,亚氯酸盐歧化酶催化过氧乙酸的反应采用了一个分步反应的机理,即:通过O-O键的均裂形成短寿命的高价态血红素氧化化合物Ⅱ(CpdⅡ)和乙酸根自由基(OAc·),之后发生从Cpd Ⅱ的卟啉环到OAc·的快速电子迁移过程,最终形成了高价态血红素氧化化合物Ⅰ(CpdⅠ)和乙酸根阴离子。第二步反应,即从Cpd Ⅱ的卟啉环到OAc·的电子过程是这个催化反应的决速步骤。计算结果指出电子迁移过程在血红素化学中的重要性,也表明了血红素酶类的反应机理真相可能被快速的电子迁移过程掩盖,即使某个重要的中间体已经被实验检测到(比如该催化反应中的Cpd Ⅰ已经被实验检测到)。与亚氯酸盐歧化酶催化亚氯酸盐(天然底物)的反应进行比较,进一步表明了血红素酶类对反应底物的敏感性,也就是说,血红素酶类催化不同的反应底物可能采用不同的反应机理。
Electron transfer(ET) is significant in heme chemistry but usually difficult to be characterized. In the present DFT calculations, a transition state for ET has been optimized during the decomposition of peracetic acid(PAA) catalyzed by chlorite dismutase(Cld). The Cld-catalyzed PPA reaction is revealed to proceed via a homolytic O-O bond cleavage to transiently form compound Ⅱ(Cpd Ⅱ) and acetate radical(OAc·), and a subsequent fast ET from Cpd Ⅱ porphyrin to OAc· leading to compound Ⅰ(Cpd Ⅰ) and acetate anion. The second step of ET from Cpd Ⅱ porphyrin to OAc· is rate-limiting. The results highlight the importance of ET in heme chemistry and imply that the reaction mechanisms of heme enzymes may be masked by fast ET even if a key intermediate has been detected(like Cpd Ⅰ in this case). The comparison with the Cld-catalyzed chlorite reaction further indicates the sensitivity of heme to substrates, that is, a heme enzyme may employ different mechanisms for different substrates.
Electron transfer(ET) is significant in heme chemistry but usually difficult to be characterized. In the present DFT calculations, a transition state for ET has been optimized during the decomposition of peracetic acid(PAA) catalyzed by chlorite dismutase(Cld). The Cld-catalyzed PPA reaction is revealed to proceed via a homolytic O-O bond cleavage to transiently form compound Ⅱ(Cpd Ⅱ) and acetate radical(OAc·), and a subsequent fast ET from Cpd Ⅱ porphyrin to OAc· leading to compound Ⅰ(Cpd Ⅰ) and acetate anion. The second step of ET from Cpd Ⅱ porphyrin to OAc· is rate-limiting. The results highlight the importance of ET in heme chemistry and imply that the reaction mechanisms of heme enzymes may be masked by fast ET even if a key intermediate has been detected(like Cpd Ⅰ in this case). The comparison with the Cld-catalyzed chlorite reaction further indicates the sensitivity of heme to substrates, that is, a heme enzyme may employ different mechanisms for different substrates.
引文
[1]Mayfield,J.A.,Béatrice,B.,Rodgers,K.R.,Lukat-Rodgers,G.S.,and Dubois,J.L.Biochemistry.2013,52:6982.
[2]Shuo,S.,Ze-Sheng,L.,and Shi-Lu,C.Dalton.T.2013,43:973.
[3]Streit,B.R.,Béatrice,B.,Lukat-Rodgers,G.S.,Rodgers,K.R.,and Dubois,J.L.J.Am.Chem.Soc.2010,132:5711.
[2]Shuo,S.,Ze-Sheng,L.,and Shi-Lu,C.Dalton.T.2013,43:973.
[3]Streit,B.R.,Béatrice,B.,Lukat-Rodgers,G.S.,Rodgers,K.R.,and Dubois,J.L.J.Am.Chem.Soc.2010,132:5711.