Qiao Chong, Chen Fei, Liu Zhan, Huang Tianfang, Li Wei, Zhang Guolin, Luo Yinggang
Center for Natural Products Research, Chengdu Institute of Biology, Chinese Academy of Sciences, Chengdu, China.
University of Chinese Academy of Sciences, Beijing, China.
Front Plant Sci. 2022 Aug 18;13:987348. doi: 10.3389/fpls.2022.987348. eCollection 2022.
Tryptophan decarboxylases (TDCs) are a group of pyridoxal 5'-phosphate-dependent enzymes involved in the enzymatic conversion of tryptophan into tryptamine, a critical biogenic amine. We herein mined and cloned a TDC-encoding gene, , from camptothecin-producing plant . The intact was heterologously overexpressed in and the recombinant CaTDC3 was purified to homogeneity. High-performance liquid chromatography (HPLC)-diode array detector (DAD) and high resolution mass spectrometry (HRMS) data analyses of the CaTDC3-catalyzed reaction mixture confirmed the catalytically decarboxylative activity of CaTDC3. CaTDC3 shows strict stereoselectivity for L-tryptophan. Homology modeling and molecular docking implied CaTDC3's recognition of L-tryptophan derivatives and analogs. Substrate scope investigations revealed that the appropriate substituent groups on the indole ring, i.e., hydroxylated and halogenated L-tryptophans, could be recognized by CaTDC3 and the decarboxylation reactions generated the corresponding tryptamines. The C -methyl-L-tryptophans were decarboxylated by CaTDC3 efficiently. 1-Thio-L-tryptophan, the NH group of the indole ring replaced by an S atom, could be decarboxylated by CaTDC3. CaTDC3 catalyzed the decarboxylation of 7-aza-L-tryptophan, an N displacement of the C on the aromatic ring, to afford 7-aza-tryptamine. L-Kynurenine, an L-tryptophan degradation product, could be decarboxylated by CaTDC3. The present works uncover a catalytically promiscuous TDC and the TDC is a versatile decarboxylase in synthetic biology for specialized pharmaceutically important substances.
色氨酸脱羧酶（TDCs）是一类依赖于5'-磷酸吡哆醛的酶，参与将色氨酸酶促转化为色胺，色胺是一种关键的生物胺。我们在此从产喜树碱的植物中挖掘并克隆了一个编码TDC的基因。完整的该基因在中进行了异源过表达，并将重组CaTDC3纯化至同质。对CaTDC3催化反应混合物的高效液相色谱（HPLC）-二极管阵列检测器（DAD）和高分辨率质谱（HRMS）数据分析证实了CaTDC3的催化脱羧活性。CaTDC3对L-色氨酸表现出严格的立体选择性。同源建模和分子对接表明CaTDC3对L-色氨酸衍生物和类似物具有识别作用。底物范围研究表明，吲哚环上合适的取代基，即羟基化和卤代的L-色氨酸，可被CaTDC3识别，脱羧反应生成相应的色胺。C-甲基-L-色氨酸能被CaTDC3高效脱羧。1-硫代-L-色氨酸，其吲哚环的NH基团被S原子取代，也能被CaTDC3脱羧。CaTDC3催化7-氮杂-L-色氨酸（芳香环上C的N取代物）脱羧生成7-氮杂色胺。L-犬尿氨酸，一种L-色氨酸降解产物，也能被CaTDC3脱羧。目前的研究揭示了一种具有催化多特异性的TDC，该TDC在合成生物学中是用于合成特殊的药学重要物质的通用脱羧酶。
