血红素依赖亚氯酸盐歧化酶催化机理的理论研究
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- 英文论文题名：Theoretical investigation of reaction mechanism of heme-dependent chlorite dismutase
- 论文作者：陈世稆 ; 苏璟璇 ; 孙硕
- 英文论文作者：Shi-Lu Chen ; Jing-Xuan Su ; Shuo Sun ; School of Chemistry ; Beijing Institute of Technology
- 年：2016
- 作者机构：北京理工大学化学学院;
- 论文关键词：酶催化机理 ; 密度泛函理论 ; 亚氯酸盐歧化酶 ; 血红素
- 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：O643.31
- 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：2
- 文件大小：321k
- 原文格式：D
- 会议级别：全国
摘要
亚氯酸盐歧化酶(Cld)是一种血红素依赖酶,能够催化毒性亚氯酸盐(ClO_2~-)的降解,生成无毒的氧气和氯离子。运用密度泛函理论,我们研究的Cld的催化机理。计算发现,反应在二重态上进行,底物通过O-Cl键均裂分解为一个低自旋三重态高价Fe(Ⅳ)=O双自由基和一个ClO~·自由基,随后发生它们之间的O-O键合。此外发现,底物的O-Cl异裂是不能发生的(Fig.1)。我们还更进一步地研究了Cld催化的非天然底物过氧乙酸(PAA)的降解机理,发现底物通过O-O键均裂分解为短寿命的化合物Ⅱ(Cpd Ⅱ)和乙酸根自由基(OAc~·),随后发生一个从Cpd Ⅱ卟啉环到OAc~·的快速电子迁移过程,生成化合物Ⅰ(Cpd Ⅰ)和乙酸根阴离子(OAc~-)(Fig.2)。其中第二步的电子迁移过程是决速步。
Chlorite dismutase(Cld) is a heme-dependent enzyme that catalyzes the decomposition of toxic chlorite(ClO_2~-) into innocuous chloride and O_2. Using the DFT B3LYP functional, the Cld reaction mechanism has been studied. The calculations indicate that the reaction proceeds along a stepwise pathway in the doublet state, i.e. a homolytic O-Cl bond cleavage of the substrate leading to a low-spin triplet-state Fe(Ⅳ)=O diradicaloid and a ClO~· radical, followed by a rebinding O-O bond formation between them. In addition, a heterolytic O-Cl bond dissociation in the initial step is shown to be unreachable. Furthermore, the Cld-catalyzed decomposition of peracetic acid(PAA, a nonnatural substrate) 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.
Chlorite dismutase(Cld) is a heme-dependent enzyme that catalyzes the decomposition of toxic chlorite(ClO_2~-) into innocuous chloride and O_2. Using the DFT B3LYP functional, the Cld reaction mechanism has been studied. The calculations indicate that the reaction proceeds along a stepwise pathway in the doublet state, i.e. a homolytic O-Cl bond cleavage of the substrate leading to a low-spin triplet-state Fe(Ⅳ)=O diradicaloid and a ClO~· radical, followed by a rebinding O-O bond formation between them. In addition, a heterolytic O-Cl bond dissociation in the initial step is shown to be unreachable. Furthermore, the Cld-catalyzed decomposition of peracetic acid(PAA, a nonnatural substrate) 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.
引文
[1]S.Sun,Z.-S.Li,S.-L.Chen,Dalton.Trans.2014,43:973.
[2]J.A.Mayfield,B.Blanc,K.R.Rodgers,G.S.Lukat-Rodgers,J.L.Du Bois,Biochemistry 2013,52:6982.
[3]B.R.Streit,B.Blanc,G.S.Lukat-Rodgers,K.R.Rodgers,J.L.Du Bois,J.Am.Chem.Soc.2010,132:5711.
[2]J.A.Mayfield,B.Blanc,K.R.Rodgers,G.S.Lukat-Rodgers,J.L.Du Bois,Biochemistry 2013,52:6982.
[3]B.R.Streit,B.Blanc,G.S.Lukat-Rodgers,K.R.Rodgers,J.L.Du Bois,J.Am.Chem.Soc.2010,132:5711.