乙酰辅酶A羧化酶（ACCase）催化底物乙酰辅酶A的羧化，是脂肪酸合成的关键限速酶。近年来，丝状不产氧光合细菌中发现的异质型ACCase不参与脂肪酸合成，而参与一种新型的3-羟基丙酸循环。该循环是自然界6种固碳途径中唯一对氧不敏感的，在3-羟基丙酸的自养生物合成中具有不可比拟的优势。然而，异质型ACCase的亚基组成、结构及在固碳中的催化机制仍然未知。基于课题组在光合细菌研究领域的积累，本项目将综合运用生物化学、结构生物学和微生物合成生物学等方法，对不产氧光合细菌中异质型ACCase的结构、催化机制和功能选择进行系统研究，阐明ACCase在3-羟基丙酸循环中固碳的催化机制，揭示异质型ACCase在生物固碳和脂肪酸合成中的协同关系，有助于揭示ACCase结构和功能的多样性和分子进化，为ACCase的合理设计、3-羟基丙酸的绿色合成及在生物固碳中的应用提供理论依据。

Acetyl-CoA carboxylase (ACCase) is a key rate-limiting enzyme in fatty acid synthesis and catalyzes the carboxylation of acetyl-CoA to malonyl-CoA. In recent years, the heteromeric ACCases found in filamentous anoxygenic phototrophs (FAPs), do not catalyze the biosynthesis of fatty acid but in the novel 3-hydroxypropionate bi-cycle. This is the only insensitive to the oxygen of six carbon fixation pathways and has incomparable advantages in autotrophic biosynthesis of 3-hydroxypropionic acid (3-HP). However, the subunit composition, structure and catalytic mechanism of heteromeric ACCase in fixing carbon are still unknown. Based on the accumulation of FAPs data in our research lab, the project will make a systematic study on the structure, catalytic mechanism and functional selection of heteromeric ACCases by comprehensively using technologies from biochemistry, structural biology, and microbial synthetic biology. It is to elucidate the function of the complex enzyme on fixing carbon in 3-hydroxypropionate cycle and analyze the synergistic relationship in carbon sequestration and fatty acids biosynthesis. The project will be helpful to reveal the structural and functional diversity and molecular evolution of heteromeric ACCases, and provides a theoretical basis for the rational design of this enzyme to the green production of 3-HP and the application of biological carbon fixation.