Sosa Max B, Leeman Jacob T, Washington Lorenzo J, Scheller Henrik V, Chang Michelle C Y
Department of Chemistry, University of California, Berkeley, Berkeley, CA 94720 USA.
Department of Plant & Microbial Biology, University of California, Berkeley, Berkeley, CA 94720 and Joint BioEnergy Institute, Lawrence Berkeley National Laboratory, Berkeley, CA 94720, USA.
bioRxiv. 2023 Dec 14:2023.12.13.571568. doi: 10.1101/2023.12.13.571568.
Amino acids (AAs) are modular and modifiable building blocks which nature uses to synthesize both macromolecules, such as proteins, and small molecule natural products, such as alkaloids and non-ribosomal peptides (NRPs). While the 20 main proteinogenic AAs display relatively limited side-chain diversity, a wide range of non-canonical amino acids (ncAAs) exist that are not used by the ribosome for protein synthesis but contain a broad array of structural features and functional groups not found in proteinogenic AAs. In this communication, we report the discovery of the biosynthetic pathway for a new ncAA, pazamine, which contains a cyclopropane ring formed in two steps. In the first step, a chlorine is added onto the C position of lysine by a radical halogenase PazA. The cyclopropane ring is then formed in the next step by a pyridoxal-5'-phosphate-dependent enzyme, PazB, via an S2-like attack onto C to eliminate chloride. Genetic studies of this pathway in the native host, , show that pazamine and its succinylated derivative, pazamide, potentially inhibit ethylene biosynthesis in growing plants based on alterations in the root phenotype of seedlings. We further show that PazB can be utilized to make an alternative cyclobutane-containing AA. These discoveries may lead to advances in biocatalytic production of specialty chemicals and agricultural biotechnology.
氨基酸（AAs）是模块化且可修饰的构建单元，自然界利用它们来合成大分子，如蛋白质，以及小分子天然产物，如生物碱和非核糖体肽（NRPs）。虽然20种主要的蛋白质ogenic氨基酸显示出相对有限的侧链多样性，但存在多种非标准氨基酸（ncAAs），它们不被核糖体用于蛋白质合成，但含有蛋白质ogenic氨基酸中未发现的广泛结构特征和官能团。在本通讯中，我们报告了一种新的ncAA——帕扎明生物合成途径的发现，它含有通过两步形成的环丙烷环。第一步，一种自由基卤化酶PazA将一个氯原子添加到赖氨酸的C位上。然后在下一步中，一种依赖于磷酸吡哆醛的酶PazB通过对C进行类似S2的攻击以消除氯离子，从而形成环丙烷环。在天然宿主中的该途径的遗传学研究表明，基于幼苗根表型的改变，帕扎明及其琥珀酰化衍生物帕扎酰胺可能抑制生长中的植物中的乙烯生物合成。我们进一步表明，PazB可用于制造一种含环丁烷的替代氨基酸。这些发现可能会推动特殊化学品的生物催化生产和农业生物技术的进步。
