集胞藻PCC6803的slr1022基因编码蛋白具有γ-氨基丁酸转氨酶和N-乙酰鸟氨酸转氨酶功能，是集胞藻PCC6803三羧酸循环中γ-氨基丁酸代谢旁路和氨基酸代谢途径中的关键酶。然而目前还没有对其底物识别分子机制及催化机理的研究报道。研究slr1022蛋白的底物识别分子机制及催化机理对于深入理解蓝细菌的三羧酸循环和氨基酸代谢途径以及探索此类转氨酶的分子进化机制都具有重要意义。本项目将以集胞藻PCC6803中slr1022蛋白为研究对象，通过分子同源建模、靶点氨基酸定点突变、酶动力学分析结合氢核磁共振、质谱分析及蛋白质结晶等技术手段系统研究slr1022蛋白的底物选择性及其结构基础，阐明slr1022蛋白作为γ-氨基丁酸转氨酶和N-乙酰鸟氨酸转氨酶的催化反应机理，为γ-氨基丁酸转氨酶和N-乙酰鸟氨酸转氨酶抑制剂的理性设计提供参考依据，同时也将为基因工程蓝细菌合成可再生生物燃料提供理论基础。

Previous study demonstrated that the protein encoded by slr1022 gene of Synechocystis sp. PCC6803 displayed the dual functions of gamma aminobutyric acid aminotransferase (GABA-AT) and N-acetylornithine aminotransferase (ArgD), which were the key enzymes in the GABA shunt of tricarboxylic acid cycle and amino acid metabolism pathway of Synechocystis sp. PCC6803, respectively. However, there was no report on the molecular mechanism of substrate specificity and catalytic mechanism of slr1022 protein yet. Studying the molecular mechanism of substrate specificity and catalytic mechanism of slr1022 protein is of great importance for understanding the tricarboxylic acid cycle and amino acid metabolism of cyanobacteria and exploring the molecular evolution mechanism of such transaminase. This project will focus on the slr1022 protein from Synechocystis sp. PCC6803. In this project, the substrate selectivity and structural basis of slr1022 as GABA-AT and ArgD will be studied systematically by homology modeling, mutagenesis, enzyme kinetic analysis combined with 1H NMR, mass spectrometry and protein crystallization technology, and the catalytic mechanism of slr1022 as GABA-AT and ArgD will be elucidated. The results of this study will not only provide reference value for the rational design of inhibitors of GABA-AT and ArgD, but also lay foundation for the production of renewable biofuels by genetically engineered cyanobacteria.