此前对集胞藻PCC6803中sll1981基因编码蛋白的功能研究存在争议。本课题组前期工作又发现sll1981蛋白具有alpha-酮戊二酸脱羧酶活性。这一发现对于深入理解集胞藻PCC6803的三羧酸循环具有重要意义。. 本项目将以sll1981蛋白为研究对象，通过体内体外酶动力学实验确定sll1981蛋白的催化底物，阐明sll1981蛋白究竟是一个催化多功能还是催化单一酶。通过测定sll1981基因缺失或过表达突变株中alpha-酮戊二酸，琥珀酸等重要代谢物的浓度验证sll1981蛋白在集胞藻PCC6803三羧酸循环中的作用，为阐明集胞藻PCC6803中alpha-酮戊二酸到琥珀酸转化途径提供生化证据。

The protein encoded by sll1981 gene of Synechocystis sp. PCC6803 was previously identified as acetolactate synthase and L-myo-inositol 1-phosphate synthase, respectively. Our preliminary result shows that sll1981 protein also functions as alpha-ketoglutarate decarboxylase, which plays a key role in the newly discovered tricarboxylic acid cycle of cyanobacteria.. In this project, the substrate catalyzed by sll1981 protein will be identified by in vivo and in vitro enzymatic kinetics and the function of sll1981 protein will be elucidated. After that, the Synechocystis sp. PCC6803 mutant strains with sll1981 gene knock out or overexpression will be constructed by gene homologous recombination technique. By measuring the concentrations of important metabolites such as alpha-ketoglutarate and succinic acid, the role of sll1981 protein in the tricarboxylic acid cycle of Synechocystis sp. PCC6803 will be identified. With that the conversion pathway of alpha-ketoglutarate to succinic acid in Synechocystis sp. PCC6803 will be proved.