代谢物损伤控制系统在消除细胞有毒代谢物、维持细胞正常生命活动中至关重要。Rid家族蛋白被认为在其中发挥重要作用。然而该蛋白家族大部分成员的催化活性和功能还不清楚，如广泛存在于细菌中的Rid6亚家族蛋白从未被研究过。尼古丁降解菌根癌土壤杆菌S33具有2套Rid6编码基因，分别位于尼古丁降解和D-氨基酸氧化基因簇上，初步实验推测它们在尼古丁和氨基酸代谢中起重要作用，代表了该家族蛋白的新功能：（1）通过水解脱氨活性解除6-羟基假氧化尼古丁和D-氨基酸氧化产生的烯胺/亚胺中间物的毒害作用；（2）通过分子伴侣活性维持6-羟基3-琥珀酰半醛吡啶脱氢酶的结构稳定和催化活性。本项目拟通过生信分析、生化测试、光谱分析和基因敲除等手段详细研究Rid6的催化机制和生理功能。这将为Rid家族蛋白在代谢物损伤控制中的作用提供新认识，有助于深入理解细胞基础代谢，为在代谢工程设计和病原微生物控制等方面应用提供理论依据。

Metabolite damage-control system plays a crucial role in dealing with toxic metabolites in vivo and maintaining the healthy metabolic activities in cells. Rid family proteins are thought to be one group of the major players during the metabolite damage-control process. However, the catalytic activity and physiological functions of the most members of the family are unknown, for example, the Rid6 subfamily proteins, widely distributed in bacteria, have not been characterized till now. We found that the nicotine-degrading Agrobacterium tumefaciens S33 harbors two sets of genes for Rid6 proteins. One is located in the nicotine-degrading gene cluster, and the other is located in the predicted D-amino acid oxidizing gene cluster. Our preliminary investigation indicated that they function in the metabolism of nicotine and D-amino acid, which are new in the functions of Rid family proteins. Their catalytic functions include: (1) to pre-empty the toxic enamine/imine intermediates produced during the oxidation of 6-hydroxypseuoxynicotine and D-amino acid by its deaminase activity; (2) to maintain the right conformation or structure and activity of 6-hydroxy-3-succinoyl-pyridine dehydrogenase by its chaperone holdase activity. In this proposal, we will characterize the catalytic mechanism and investigate the physiological function of Rid6 family proteins by bioinformatic analysis, biochemical assay, spectral analysis, and gene knock-out. This study will provide new insights of the function of Rid family protein in metabolite damage-control system and help to understand the basic metabolism in cells, which would be helpful for their application in pathogens control and metabolic engineering in the near future.