The 2.0 Å crystal structure of catalase-peroxidase from Haloarcula marismortui
The 2.0 Å crystal structure of catalase-peroxidase from Haloarcula marismortui
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DOI：
10.1038/nsb834
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发表时间：
2002-09-01
期刊：
影响因子：
--
通讯作者：
Tanaka, N
中科院分区：
文献类型：
--
作者：
Yamada, Y;Fujiwara, T;Tanaka, N
过氧化氢酶-过氧化物酶是I类过氧化物酶超家族的成员。该酶同时具有过氧化氢酶和过氧化物酶活性，可以从活细胞中清除有害的过氧化氢分子。Haloarcula marismortui(HmCP)过氧化氢酶过氧化物酶(HmCP)的2.0埃晶体结构表明，该酶是由两个相同亚基组成的二聚体。每个亚基由两个结构上同源的结构域组成，其拓扑结构类似于I类过氧化物酶。HmCP的活性部位位于N-末端结构域。尽管催化残基和辅因子血红素在活性部位的排列实际上与I类过氧化物酶的排列相同，但血红素部分埋在结构域中，类似于典型的过氧化氢酶。在活性中心附近，三个残基的侧链之间形成了新的共价键，包括血红素远端的色氨酸侧链。与C-末端结构域一起，这些共价键在酶的表面固定两个长环，覆盖到活性部位的底物通道。这些特征为该酶的双重活性提供了解释。
Catalase-peroxidase is a member of the class I peroxidase superfamily. The enzyme exhibits both catalase and peroxidase activities to remove the harmful peroxide molecule from the living cell. The 2.0 Angstrom crystal structure of the catalase-peroxidase from Haloarcula marismortui (HmCP) reveals that the enzyme is a dimer of two identical subunits. Each subunit is composed of two structurally homologous domains with a topology similar to that of class I peroxidase. The active site of HmCP is in the N-terminal domain. Although the arrangement of the catalytic residues and the cofactor heme bin the active site is virtually identical to that of class I peroxidases, the heme moiety is buried inside the domain, similar to that in a typical catalase. In the vicinity of the active site, novel covalent bonds are formed among the side chains of three residues, including that of a tryptophan on the distal side of the heme. Together with the C-terminal domain, these covalent bonds fix two long loops on the surface of the enzyme that cover the substrate access channel to the active site. These features provide an explanation for the dual activities of this enzyme.