Nα-acetyl-α-lysine合成关键酶及其特异性催化机制的研究

Nα-acetyl-α-lysine是一种新型相容性溶质，能够抵御外界渗透压胁迫，同时具有在干旱、高温等逆境中保护细胞和生物大分子的作用。Nα-acetyl-α-lysine的生物合成还未有报道。在前期工作中我们基本确定了Nα-acetyl-α-lysine的生物合成途径，但其中的关键乙酰基转移酶还未找到。本研究拟从Nα-acetyl-α-lysine在菌株S.halodurans H3B36中具有热保护作用现象为出发点，通过对其转录组差异基因的分析以及基因的异源表达，确定其合成的关键酶；进一步对该基因所编码的蛋白进行表达纯化，研究这一新酶源的酶学性质及动力学参数；从氨基酸序列、酶结构比对和突变分析等层面上，探讨和揭示其底物结合和催化作用模式，通过蛋白晶体培养和结构解析研究其底物专一性，为构建抗逆菌株和农作物提供新资源和改造策略。

Nα-acetyl-α-lysine is a new type of compatible solute that helps cells against salinity stresses and can protect cells and biological macromolecules in severe environments, like drought, high temperature, etc. The synthesis pathway and the mechanism of Nα-acetyl-α-lysine accumulation are unclear. Until recently, we found the general synthesis pathway of Nα-acetyl-α-lysine. However, a key enzyme, acetyltransferase, involved in this process is unknown. Taking the phenomenon that Nα-acetyl-α-lysine exhibited heat stress-relieving property as a breakthrough, transcriptomics will be applied to get different intracellular gene expression profiles of strain S.halodurans H3B36. Based on bioinformatics database and statistical software, the key synthesis genes will be achieved. We will also reveal the novel mechanism of substrate binding and catalysis by genes and structure comparison, crystal structure resolving, sequence and mutagenesis analysis. The results will provide new enzyme resources. And this work will also be significant to enzyme engineering and molecular design of crop for industrial application under extreme conditions.