Crystal structures of α-dioxygenase from Oryza sativa: insights into substrate binding and activation by hydrogen peroxide.
Crystal structures of α-dioxygenase from Oryza sativa: insights into substrate binding and activation by hydrogen peroxide.
复制标题
稻α-双加氧酶的晶体结构：深入了解过氧化氢的底物结合和激活。
DOI：
10.1002/pro.2327
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发表时间：
2013
期刊：
影响因子：
--
通讯作者：
Malkowski,MichaelG
中科院分区：
文献类型：
--
作者：
Zhu,Guangyu;Koszelak-Rosenblum,Mary;Malkowski,MichaelG
α‐Dioxygenases (α‐DOX) are heme‐containing enzymes found predominantly in plants and fungi, where they generate oxylipins in response to pathogen attack. α‐DOX oxygenate a variety of 14–20 carbon fatty acids containing up to three unsaturated bonds through stereoselective removal of thepro‐Rhydrogen from the α‐carbon by a tyrosyl radical generated via the oxidation of the heme moiety by hydrogen peroxide (H2O2). We determined the X‐ray crystal structures of wild type α‐DOX fromOryza sativa, the wild type enzyme in complex with H2O2, and the catalytically inactive Y379F mutant in complex with the fatty acid palmitic acid (PA). PA binds within the active site cleft of α‐DOX such that the carboxylate forms ionic interactions with His‐311 and Arg‐559. Thr‐316 aids in the positioning of carbon‐2 for hydrogen abstraction. Twenty‐five of the twenty eight contacts made between PA and residues lining the active site occur within the carboxylate and first eight carbons, indicating that interactions within this region of the substrate are responsible for governing selectivity. Comparison of the wild type and H2O2structures provides insight into enzyme activation. The binding of H2O2at the distal face of the heme displaces residues His‐157, Asp‐158, and Trp‐159 ∼2.5 Å from their positions in the wild type structure. As a result, the Oδ2 atom of Asp‐158 interacts with the Ca atom in the calcium binding loop, the side chains of Trp‐159 and Trp‐213 reorient, and the guanidinium group of Arg‐559 is repositioned near Tyr‐379, poised to interact with the carboxylate group of the substrate.
