PTS山梨糖醇系统介导的水苏糖促嗜酸乳杆菌增殖机制研究

水苏糖是一种可选择性促肠道益生菌增殖的益生元，应用前景广阔。申请人前期研究发现，以水苏糖为单一碳源培养嗜酸乳杆菌时，其磷酸转移酶山梨糖醇系统（PTS系统）酶II、α-半乳糖苷酶和蔗糖酶表达升高，提示：水苏糖是经PTS山梨糖醇系统跨膜转运，进入胞内，被相关酶依次降解代谢，实现促嗜酸乳杆菌增殖，但具体作用机制仍不明确。本项目拟基于PTS山梨糖醇系统深入研究水苏糖在嗜酸乳杆菌中的跨膜转运及代谢途径，全面解析水苏糖促嗜酸乳杆菌增殖机制。研究内容包括：从跨膜蛋白与水苏糖结合模式预测、跨膜转运过程解析、PTS山梨糖醇系统功能验证等方面，阐明PTS山梨糖醇系统跨膜转运水苏糖的过程；围绕水苏糖代谢产物-棉籽糖降解的歧化性，探究水苏糖代谢产物及相关酶，揭示水苏糖在嗜酸乳杆菌中的完整代谢途径。为阐述低聚糖跨膜转运机制提供重要研究思路及方法，为益生菌、益生元类健康食品研发升级与拓展提供重要科学依据。

Stachyose is one of prebiotic oligosaccharides which could promote the proliferation of probiotic bacteria in an intestinal tract. In our previous study, comparative proteomic analysis revealed the sorbitol phosphotransferase system (PTS system) enzyme II, α-galactosidase and invertase of L. acidophilus, were overexpressed in the medium with stachyose as sole carbon source. It suggests stachyose might be transported into the cytoplasm by sorbitol PTS system. Meanwhile, the catabolism of stachyose can provide energy to the proliferation of L.acidophilus. Therefore, the mechanism of stachyose transmembrane transport and catabolism mediated by PTS system in L.acidophilus will be investigated in the proposed study. The specific research items are mainly described as follows: based on the binding mode of transmembrane protein, stachyose transmembrane transport process, and the function of sorbitol PTS system, the mechanisms of stachyose transmembrane transport mediated by sorbitol PTS system in L. acidophilus will be explored. New insights will be provided for the transport of other oligosaccharides across the membrane. Catabolic pathway of stachyose in L. acidophilus will be revealed by detecting its intermediate metabolites and related enzyme, which may benefit research and development of stachyose and probiotics-involved functional foods.