Implications for the catalytic mechanism of the vanadium-containing enzyme chloroperoxidase from the fungus Curvularia inaequalis by X-ray structures of the native and peroxide form
Implications for the catalytic mechanism of the vanadium-containing enzyme chloroperoxidase from the fungus Curvularia inaequalis by X-ray structures of the native and peroxide form
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DOI：
10.1515/bchm.1997.378.3-4.309
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发表时间：
1997-03-01
影响因子：
3.7
通讯作者：
Wever, R
中科院分区：
文献类型：
--
作者：
Messerschmidt, A;Prade, L;Wever, R
从真菌曲霉含钒氯过氧化物酶的天然和过氧化形式的晶体结构得到了该酶催化机制的启示。利用叠氮化物氯过氧化物酶配合物的原子模型，用差分傅立叶技术求解了x射线结构。天然酶的2.03埃晶体结构（R = 19.7%）揭示了完整的催化钒中心的几何形状。钒由组氨酸496中的4个非蛋白氧原子和1个氮（NE2）原子以三角双锥体方式配位。三个氧原子在赤道面上第四个氧原子和氮原子在双金字塔的顶端。在过氧化物衍生物的2.24埃晶体结构（R = 17.7%）中，在顶端氧配体释放后，过氧化物以eta(2)-方式与钒结合。钒还与组氨酸496中的4个非蛋白氧原子和1个氮（NE2）配位。钒周围的配位几何是一个扭曲的四边形金字塔，两个过氧，一个氧和氮在基面上，一个氧在顶端位置。基于这些x射线结构和动力学数据，提出了催化循环的机理。
Implications for the catalytic mechanism of the vanadium-containing chloroperoxidase from the fungus Curvularia inaequalis have been obtained from the crystal structures of the native and peroxide forms of the enzyme. The X-ray structures have been solved by difference Fourier techniques using the atomic model of the azide chloroperoxidase complex. The 2.03 Angstrom crystal structure (R = 19.7%) of the native enzyme reveals the geometry of the intact catalytic vanadium center. The vanadium is coordinated by four non-protein oxygen atoms and one nitrogen (NE2) atom from histidine 496 in a trigonal bipyramidal fashion. Three oxygens are in the equatorial plane and the fourth oxygen and the nitrogen are at the apexes of the bipyramid. In the 2.24 Angstrom crystal structure (R = 17.7%) of the peroxide derivate the peroxide is bound to the vanadium in an eta(2)-fashion after the release of the apical oxygen ligand. The vanadium is coordinated also by 4 non-protein oxygen atoms and one nitrogen (NE2) from histidine 496. The coordination geometry around the vanadium is that of a distorted tetragonal pyramid with the two peroxide oxygens, one oxygen and the nitrogen in the basal plane and one oxygen in the apical position. A mechanism for the catalytic cycle has been proposed based on these X-ray structures and kinetic data.