Structural Basis of Enzymatic (S)-Norcoclaurine Biosynthesis
Structural Basis of Enzymatic (S)-Norcoclaurine Biosynthesis
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DOI：
10.1074/jbc.m803738200
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发表时间：
2009-01-09
影响因子：
4.8
通讯作者：
Boffi, Alberto
中科院分区：
文献类型：
--
作者：
Ilari, Andrea;Franceschini, Stefano;Boffi, Alberto
去甲乌药碱合成酶（NCS）催化多巴胺和4-羟基苯乙醛之间的立体特异性Pictet-Spengler环化，这是苄基异喹啉生物碱生物合成途径中的关键步骤。在2.1埃分辨率下，解析了来自黄菊的去甲乌药碱合酶与多巴胺底物和非反应性底物类似物4-羟基苯甲醛的复合物的晶体结构。NCS与催化吲哚生物碱途径的第一步的功能相关的“Pictet-Spenglerases”没有共同的特征，并且符合Bet v1样蛋白的整体折叠。NCS的活性位点位于20埃长的催化通道内，由酪氨酸、赖氨酸、天冬氨酸和谷氨酸的侧链形成。氨基酸侧链相对于底物的几何形状揭示了支配立体选择性Pictet-Spengler环化机制的结构决定因素，从而为理解催化过程的更精细细节奠定了良好的基础。相关残基的定点突变证实了基于晶体学结果的分配。
The enzyme norcoclaurine synthase (NCS) catalyzes the stereospecific Pictet-Spengler cyclization between dopamine and 4-hydroxyphenylacetaldehyde, the key step in the benzylisoquinoline alkaloid biosynthetic pathway. The crystallographic structure of norcoclaurine synthase from Thalictrum flavum in its complex with dopamine substrate and the nonreactive substrate analogue 4-hydroxybenzaldehyde has been solved at 2.1 angstrom resolution. NCS shares no common features with the functionally correlated "Pictet-Spenglerases" that catalyze the first step of the indole alkaloids pathways and conforms to the overall fold of the Bet v1-like protein. The active site of NCS is located within a 20-angstrom-long catalytic tunnel and is shaped by the side chains of a tyrosine, a lysine, an aspartic, and a glutamic acid. The geometry of the amino acid side chains with respect to the substrates reveals the structural determinants that govern the mechanism of the stereoselective Pictet-Spengler cyclization, thus establishing an excellent foundation for the understanding of the finer details of the catalytic process. Site-directed mutations of the relevant residues confirm the assignment based on crystallographic findings.