Crystal structure of LAAO from Calloselasma rhodostoma with an L-phenylalaniine substrate:: Insights into structure and mechanism
Crystal structure of LAAO from Calloselasma rhodostoma with an L-phenylalaniine substrate:: Insights into structure and mechanism
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DOI：
10.1016/j.jmb.2006.09.032
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发表时间：
2006-12-15
影响因子：
5.6
通讯作者：
Vrielink, Alice
中科院分区：
文献类型：
--
作者：
Moustafa, Ibrahim M.;Foster, Scoff;Vrielink, Alice
L-氨基酸氧化酶是一种二聚体糖基化黄素酶，是红口蛇毒的主要成分。该酶表现出细胞凋亡诱导作用以及抗菌和抗HIV活性。L-氨基酸氧化酶及其底物（L-苯丙氨酸）的结构已被细化到1.8埃的分辨率。复合物结构揭示了与还原黄素（FAD（红色））结合的底物。关键残基His 223和Arg 322的替代构象是明显的，表明动态活性位点。此外，构象变化是明显的异咯嗪环;三环系统表现出更多的弯曲N5-N10轴相比，氧化黄素。所观察到的动力学的催化机制的影响进行了讨论。在酶的掩埋表面的检查揭示了Y形通道系统从蛋白质的外表面延伸到活性位点。该通道的一部分可作为氧化半反应期间O-2的进入路径。第二个区域，从建议的O-2通道分离的N末端（残基8-16）的蛋白质，可能在过氧化氢的释放中发挥作用。有趣的是，通道的后一部分将H2 O2产物引导到蛋白质的外表面，靠近聚糖部分;被认为将酶锚在宿主细胞上。这种通道定位可能解释了酶将H2 O2定位于靶细胞并因此诱导凋亡效应的能力。(c)2006爱思唯尔有限公司保留所有权利。
L-Amino acid oxidase is a dimeric glycosylated flavoenzyme, a major constituent of the venom-from the snake Calloselasma rhodostoma. The enzyme exhibits apoptosis inducing effects as well as antibacterial and anti-HIV activities. The structure of L-amino acid oxidase with its substrate (L-phenylalanine) has been refined to a resolution of 1.8 angstrom. The complex structure reveals the substrate bound to the reduced flavin (FAD(red)). Alternative conformations for the key residues His223 and Arg322 are evident, suggesting a dynamic active site. Furthermore, conformational changes are apparent for the isoalloxazine ring; the three-ring system exhibits more bending around the N5-N10 axis compared to the oxidized flavin. The implications of the observed dynamics on the mechanism of catalysis are discussed. Inspection of buried surfaces in the enzyme reveals a Y-shaped channel system extending from the external surface of the protein to the active site. One portion of this channel may serve as the entry path for O-2 during the oxidative half-reaction. The second region, separated from the proposed O-2 channel by the N terminus (residues 8-16) of the protein, may play a role in H2O2 release. Interestingly, the latter portion of the channel would direct the H2O2 product to the exterior surface of the protein, near the glycan moiety; thought to anchor the enzyme to the host cell. This channel location may explain the ability of the enzyme to localize H2O2 to the targeted cell and thus induce the apoptotic effect. (c) 2006 Elsevier Ltd. All rights reserved.