Structural elucidation of chalcone reductase and implications for deoxychalcone biosynthesis
Structural elucidation of chalcone reductase and implications for deoxychalcone biosynthesis
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DOI：
10.1074/jbc.m502239200
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发表时间：
2005-08-26
影响因子：
4.8
通讯作者：
Noel, JP
中科院分区：
文献类型：
--
作者：
Bomati, EK;Austin, MB;Noel, JP
4,2', 4', 6'-四羟基查尔酮（查尔酮）和4,2',4'-三羟基查尔酮（脱氧查尔酮）是具有重要生态意义的类黄酮和异黄酮的前体。脱氧查尔酮的形成依赖于查尔酮合成酶和查尔酮还原酶；然而，在查尔酮合成酶催化的多步反应中形成的可能底物中，查尔酮还原酶底物的身份仍然是实验上难以捉摸的。本文报道了苜蓿查尔酮还原酶与NADP（+）辅因子结合的三维结构，并提出了其底物的身份和结合方式，即查尔酮合成酶催化的完全延伸的香马尔酮四肽硫酯中间体的非芳构化香马尔酮三酮中间体。在没有三元配合物的情况下，精制NADP（+）结合查尔酮还原酶结构的质量可作为计算机辅助对接的模板，以评估可能底物的可能性。有趣的是，查尔酮还原酶采用aldo/keto还原酶超家族的三维结构。aldo/酮还原酶折叠在结构上不同于所有已知的脂肪酸生物合成的酮还原酶，而属于短链脱氢酶/还原酶超家族。本文的研究结果为这两种酮还原酶的趋同功能进化提供了结构支持，这两种酶在脂肪酸/聚酮的生物合成中具有相似的作用。此外，查尔酮还原酶结构是aldo/ketoreductase 4家族成员的第一个蛋白质结构。因此，查尔酮还原酶结构可以作为其他aldo/ketoreductase 4家族成员的同源性建模模板，包括参与吗啡生物合成的还原酶，即可待因酮还原酶。
4,2', 4', 6'-tetrahydroxychalcone (chalcone) and 4,2', 4'-trihydroxychalcone ( deoxychalcone) serve as precursors of ecologically important flavonoids and isoflavonoids. Deoxychalcone formation depends on chalcone synthase and chalcone reductase; however, the identity of the chalcone reductase substrate out of the possible substrates formed during the multistep reaction catalyzed by chalcone synthase remains experimentally elusive. We report here the three-dimensional structure of alfalfa chalcone reductase bound to the NADP(+) cofactor and propose the identity and binding mode of its substrate, namely the non-aromatized coumaryl-trione intermediate of the chalcone synthase-catalyzed cyclization of the fully extended coumaryl-tetraketide thioester intermediate. In the absence of a ternary complex, the quality of the refined NADP(+)-bound chalcone reductase structure serves as a template for computer-assisted docking to evaluate the likelihood of possible substrates. Interestingly, chalcone reductase adopts the three-dimensional structure of the aldo/keto reductase superfamily. The aldo/keto reductase fold is structurally distinct from all known ketoreductases of fatty acid biosynthesis, which instead belong to the short-chain dehydrogenase/reductase superfamily. The results presented here provide structural support for convergent functional evolution of these two ketoreductases that share similar roles in the biosynthesis of fatty acids/polyketides. In addition, the chalcone reductase structure represents the first protein structure of a member of the aldo/ketoreductase 4 family. Therefore, the chalcone reductase structure serves as a template for the homology modeling of other aldo/ketoreductase 4 family members, including the reductase involved in morphine biosynthesis, namely codeinone reductase.