Structural basis for divergent and convergent evolution of catalytic machineries in plant aromatic amino acid decarboxylase proteins
Structural basis for divergent and convergent evolution of catalytic machineries in plant aromatic amino acid decarboxylase proteins
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DOI：
10.1073/pnas.1920097117
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发表时间：
2020-05-19
影响因子：
11.1
通讯作者：
Weng, Jing-Ke
中科院分区：
文献类型：
--
作者：
Torrens-Spence, Michael P.;Chiang, Ying-Chih;Weng, Jing-Ke
植物吡哆醛5 '-磷酸（PLP）依赖的芳香族L-氨基酸脱羧酶（AAAD）家族的辐射产生了一系列表现出不同底物偏好和催化机制的旁系同源酶。植物AAAD催化芳香族L-氨基酸的脱羧或脱羧依赖性氧化脱氨，分别产生芳香族单胺或芳香族乙醛。这些化合物作为几类重要的植物天然产物的生物合成的关键前体，包括吲哚生物碱、苄基异喹啉生物碱、羟基肉桂酸酰胺、苯乙酰丙酮衍生的花挥发物和酪醇衍生物。在这里，我们提出了四个功能不同的植物AAAD旁系同源物的晶体结构。通过结构和功能分析，我们确定了可变的结构特征的底物结合口袋的基础上的底物选择性对吲哚，苯基，或羟苯基氨基酸在植物AAAD的分歧演变。此外，我们描述了两个机制类独立产生的突变AAAD旁系同源物导致收敛进化的衍生醛合酶活性。应用从这项研究中学到的知识，我们成功地设计了一个缩短的苄基异喹啉生物碱途径，在酵母中生产（S）-去甲乌药碱。这项工作突出了AAAD折叠的柔韧性，其允许改变底物选择性并仅用几个突变获得替代催化机制。
Radiation of the plant pyridoxal 5'-phosphate (PLP)-dependent aromatic L-amino acid decarboxylase (AAAD) family has yielded an array of paralogous enzymes exhibiting divergent substrate preferences and catalytic mechanisms. Plant AAADs catalyze either the decarboxylation or decarboxylation-dependent oxidative deamination of aromatic L-amino acids to produce aromatic monoamines or aromatic acetaldehydes, respectively. These compounds serve as key precursors for the biosynthesis of several important classes of plant natural products, including indole alkaloids, benzylisoquinoline alkaloids, hydroxycinnamic acid amides, phenylacetaldehyde-derived floral volatiles, and tyrosol derivatives. Here, we present the crystal structures of four functionally distinct plant AAAD paralogs. Through structural and functional analyses, we identify variable structural features of the substrate-binding pocket that underlie the divergent evolution of substrate selectivity toward indole, phenyl, or hydroxyphenyl amino acids in plant AAADs. Moreover, we describe two mechanistic classes of independently arising mutations in AAAD paralogs leading to the convergent evolution of the derived aldehyde synthase activity. Applying knowledge learned from this study, we successfully engineered a shortened benzylisoquinoline alkaloid pathway to produce (S)-norcoclaurine in yeast. This work highlights the pliability of the AAAD fold that allows change of substrate selectivity and access to alternative catalytic mechanisms with only a few mutations.