PDF(Pubmed)
Abstract：
Homologation of amino acids is the insertion or deletion of a methylene group to their side chain, which is a relatively uncommon chemical transformation observed in peptide natural product (NP) structure. Homologated amino acids can potentially make the NP more stable in a biological system, but its biosynthesis is yet to be understood. This study biochemically characterized the first of three unexplored enzymes in the homologation pathway of l-phenylalanine and l-tyrosine. Previously proposed reactions catalyzed by HphA were confirmed by reversed-phase high-performance liquid chromatography and tandem mass spectrometry analysis. The substrate profile and kinetic parameters showed high selectivity for the natural substrates and their close analogs. The comparability of HphA to homologous enzymes in primary metabolic pathways, 2-isopropylmate synthase and homocitrate synthase which are involved in l-leucine and l-lysine biosynthesis, respectively, was validated by bioinformatical and site-directed mutagenesis studies. The knowledge obtained from this study has deepened the understanding of the homologation of amino acids, which can lead to future combinatorial biosynthesis and metabolic engineering studies.
摘要：
氨基酸的同源是在其侧链上插入或缺失亚甲基，这是在肽天然产物(NP)结构中观察到的相对不常见的化学转化。同源氨基酸可以使NP在生物系统中更稳定，但其生物合成尚待了解。这项研究在生物化学上表征了1-苯丙氨酸和1-酪氨酸同源途径中三种未开发的酶中的第一种。先前提出的由HphA催化的反应通过反相高效液相色谱和串联质谱分析得到证实。底物概况和动力学参数显示出对天然底物及其紧密类似物的高选择性。HphA与主要代谢途径中同源酶的可比性，参与l-亮氨酸和l-赖氨酸生物合成的2-异丙基合酶和高柠檬酸合酶，分别,通过生物信息学和定点诱变研究进行了验证。从这项研究中获得的知识加深了对氨基酸同源的理解，这可以导致未来的组合生物合成和代谢工程研究。
