模拟含双锌核的甲烷单加氧酶催化甲烷和乙烷羟基化理论研究  

Theoretical study on methane and ethane hydroxylation by mimic methane monooxygenase with bis(μ-oxo)dimanganese core

作　　者：徐建[1] 高超[1] 杨华清[1] 秦松[2] 胡常伟[2] 

机构地区：[1]四川大学化工学院,四川成都610065 [2]四川大学化学学院,四川成都610064

出　　处：《化学研究与应用》2009年第6期877-882,共6页Chemical Research and Application

基　　金：国家自然科学基金资助项目(20503017)

摘　　要：采用密度泛函B3LYP方法,研究含双锌核的甲烷单加氧酶催化底物CH3X(X=H,CH3)羟基化的反应机理。用cis-(HCOO)(C3N2H4)Zn2(μ-O)2(COOH)(C3N2H4)(其中C3N2H4=咪唑)模拟双锌核甲烷单加氧酶中的关键化合物Q。研究表明,反应通过自由基回弹机理发生。首先,底物CH3X(X=H,CH3)与Q中的一个桥形氧发生相互作用生成分子复合物QCH3X。然后,Q中的一个桥形氧进一步夺取底物中的氢原子,生成QH和XCH2双自由基。这两种双自由基很容易结合生成醇类分子复合物PXCH2OH,其中P=cis-(HCOO)(C3N2H4)Zn(μ-O)Zn(COOH)(C3N2H4)。最后,分子复合物PXCH2OH脱去羟基化合物XCH2OH生成P。在298.15K和1atm的条件下,含双锌核甲烷单加氧酶Q催化CH4和CH3CH3羟基化反应在蛋白质溶液中的速率常数分别为6.414×10-19和1.542×10-6dm3.mol-1.s-1。The reaction mechanism for CH3 X （ X = H, CH3 ） hydroxylation catalyzed by methane monooxygenase （MMO） with dizinc core has been investigated by density functional method B3LYP. The key reactive compound Q of MMO is modeled by cis（HCOO） （C3 N2H4 ）Zn（μ-O）2Zn（ COOH ）（ C3N2H4 ）. The reaction is shown to proceed via a bound-radical mechanism. Firsdy, the substrate CH3 X （X = H, CH3 ） interacts with one bridge oxygen in Q,leading to form the molecular complex QCH3 X. Secondly, the reaction goes over the H-abstraction transition state to form biradical [ QH and XCH2 ], and these two radicals may spontaneously combine to give the molecular complex PXCH2 OH, P = cis- （HCOO） （ C3 N2 H4 ） Zn （ μ-O ） Zn （COOH） （ C3 N2 H4 ）. Lastly, the hydroxyl compound, XCH2 OH, may release from PXCH2 OH, leaving on the product P. The rate constants for the formation of CH3OH and CH3CH2OH in protein solution are predicted to be 6. 414 × 10^19 and 1. 542 × 10^-6 dm^3 .mol^-1·s^-1 under the 298.15 K temperature and 1 arm pressure.

关 键 词：密度泛函方法 双锌核甲烷单加氧酶 自由基机理 羟基化合物 

分 类 号：O641.121[理学—物理化学]