Study on the fusion expression of L-rhamnose-isomerase and D-psicose-3-epimerase

Abstract

D-Allose, a rare cis-aldohexose with extensive physiological functions, has significant applications in food, healthcare, and pharmaceutical fields. Particularly due to its remarkable anticancer activity and adjuvant effects in cancer radiotherapy/chemotherapy, it has become a research hotspot. Current production methods primarily utilize D-psicose as substrate with L-rhamnose isomerase (L-RhI) as catalyst for direct synthesis. However, the process faces substantial economic constraints due to the market scarcity of D-psicose. This study addressed the high-cost issues in existing production systems by successfully achieving the co-expression of D-psicose 3-epimerase (DPEase) and L-rhamnose isomerase (L-RhI) in the E. coli BL21(DE3) host using the pETDuet-1 dual-expression vector. SDS-PAGE analysis confirmed the stable expression of two active proteins with molecular weights of 35 kDa (DPEase) and 45 kDa (L-RhI), respectively. This research establishes theoretical foundations for developing a bioconversion pathway to produce D-allose from the economical substrate D-fructose.