过氧化氢酶催化梭曼水解机理的FTIR研究

FTIR STUDY OF THE CATALYTIC MECHANISM OF CATALASE ON THE HYDROLYSIS OF SOMAN

利用傅里叶交换红外光谱法（ＦＴＩＲ）分析了过氧化氢酶在溶液中的二级结构和过氧化氢酶与过氧化氢、叠氮化钠以及梭曼作用后酶结构的不同改变，并比较了梭曼与细胞色素Ｃ和糜蛋白酶作用的结果。说明过氧化氢酶作为一种氧伦还原酶使过氧化氢分解或与叠氮化钠结合时，不导致酶空间结构的明显改变；但作为一种水解酶与梭曼反应后则出现酶分子的正常β－折叠结构降低和分子间聚合，而其构象变化与梭曼抑制糜蛋白酶的反应相似，揭示了过氧化酶催化梭曼水解机理的重要信息。

Catalase can catalyze the hydrolysis of organophosphorous compounds as well as the decomposition of hydrogen peroxide,but the catalytic mechanisms may be different.Using Fourier transform infrared(FTIR) spectroscopy, the secondary structure of catalase from Micrococus lysodeikticus in D2O solution was studied and then the conformational changes of catalase after reaction with H2O2,NaN3 and soman were compared.Additionally,the effects of soman on the conformation of cytochrome C and chymotrypsin were investigated.Curve-fitting of the deconvoluted amide I band of catalase revealed 29.8% α-helical, 34.2%β-sheet,16.9% turn and 19.1% unordered structures. After reacted with H2O2 as well as NaN3,the specific catalytic inhibitor of hydrogen peroxide,catalase did not show any structural changes.It means that binding at this active site of catalase does not induce any structural modifications. However,the structural characteristics of catalase after reaction with soman indicate the involvement of conformational adjustment in the formation of a complex compound,which is similar to the reaction of soman with chymotrypsin and characteristic of a hydrolase catalytic mechanism.and this reveals important information in the hydrolysis of soman by catalase.