Inhibitor coordination interactions in the binuclear manganese cluster of arginase
Inhibitor coordination interactions in the binuclear manganese cluster of arginase
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DOI：
10.1021/bi0491705
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发表时间：
2004-07-20
期刊：
影响因子：
2.9
通讯作者：
Christianson, DW
中科院分区：
文献类型：
--
作者：
Cama, E;Pethe, S;Christianson, DW
精氨酸酶是一种锰金属酶，它催化l -精氨酸水解生成l -鸟氨酸和尿素。双核锰簇的结构和稳定性对催化活性至关重要，因为它可以激活催化亲核试剂、金属桥接氢氧化物离子，并稳定四面体中间体及其侧链状态。在这里，我们报道了一系列与精氨酸酶活性位点结合的抑制剂的x射线结构，每种抑制剂利用与Mn-2（2+）簇的不同配位模式。具体来说，我们研究了氟离子（F-；一种非竞争性抑制剂）与l -精氨酸、l -缬氨酸、二-no -羟基- l -精氨酸、去羧基-非-n - ω -羟基- l -精氨酸和脱氢-2(S)-氨基-6-硼化硼酸的结合。一些抑制剂，如氟离子、二- n- ω -羟基- l -精氨酸和脱氢-2(S)-氨基-6-硼己酸，会导致Mn-2（2+）簇上净添加一个配体。其他抑制剂，如去羧基-非n - ω -羟基- l-精氨酸，只是取代天然酶的金属桥接氢氧化物离子，不会引起金属配位多面体的任何净变化。亲和力最高的抑制剂取代了金属桥接的氢氧化物离子（有时占据了天然酶中空缺的Mn-A（2+）位点），并与α -氨基和-羧酸基保持保守的氢键阵列。
Arginase is a manganese metalloenzyme that catalyzes the hydrolysis Of L-arginine to form L-ornithine and urea. The structure and stability of the binuclear manganese cluster are critical for catalytic activity as it activates the catalytic nucleophile, metal-bridging hydroxide ion, and stabilizes the tetrahedral intermediate and its flanking states. Here, we report X-ray structures of a series of inhibitors bound to the active site of arginase, and each inhibitor exploits a different mode of coordination with the Mn-2(2+) cluster. Specifically, we have studied the binding of fluoride ion (F-; an uncompetitive inhibitor) and L-arginine, L-valine, dinor-NO-hydroxy-L-arginine, descarboxy-nor-N-omega-hydroxy-L-arginine, and dehydro-2(S)-amino-6-boronchexanoic acid. Some inhibitors, such as fluoride ion, dinor-N-omega-hydroxy-L-arginine, and dehydro-2(S)-amino-6-boronohexanoic acid, cause the net addition of one ligand to the Mn-2(2+) cluster. Other inhibitors, such as descarboxy-nor-N-omega-hydroxy-L-arginine, simply displace the metal-bridging hydroxide ion of the native enzyme and do not cause any net change in the metal coordination polyhedra. The highest affinity inhibitors displace the metal-bridging hydroxide ion (and sometimes occupy a Mn-A(2+) site found vacant in the native enzyme) and maintain a conserved array of hydrogen bonds with their alpha-amino and -carboxylate groups.