Branched‐Chain Amino Acids Mediate the Regulation of SACE_Lrp on the Aminotransferase IlvE Involved in Erythromycin Biosynthesis in Saccharopolyspora erythraea

Erythromycin is a broad-spectrum polyketide antibiotic which can be obtained mainly through biosynthesis. The catabolic pathway of branched-chain amino acids (BCAAs) significantly influences the biosynthesis of erythromycin. However, the regulatory mechanisms controlling the BCAA catabolic pathway in actinobacteria remain poorly understood, particularly in key industrial antibiotics-producing actinobacteria. This study investigates the role of BCAA aminotransferase IlvE controlled by an Lrp-family regulator SACE_Lrp in erythromycin biosynthesis and enhances erythromycin yield through a coupled strategy involving regulator manipulation and BCAA supplementation. In this work, we demonstrated that SACE_Lrp directly controlled the expression of ilvE in the presence of BCAAs, and BCAA supplementation promoted the binding of SACE_Lrp to the ilvE promoter in vivo and in vitro. BCAAs addition results in a higher increase of ilvE transcription and erythromycin production in ΔSACE_Lrp than in Saccharopolyspora erythraea A226. Gene disruption of ilvE in S. erythraea A226 resulted in a 63% decrease in erythromycin production, while overexpression of ilvE in A226 and Streptomyces coelicolor M145 enhanced erythromycin and actinorhodin production by 74% and 58%, respectively. Furthermore, overexpression of ilvE in the industrial strain S. erythraea WB (WB/pIB-ilvE) and WBΔSACE_Lrp/5387-5386 (WBΔSACE_Lrp/5387-5386-ilvE) led to 28%, and 48% increase in erythromycin production, respectively, compared to WB. Additionally, supplementation with 30 mM valine in WBΔSACE_Lrp/5387-5386-ilvE cultures further increased total erythromycin production by 71%. This work expands the understanding of the role of SACE_Lrp in the molecular regulation of antibiotic biosynthesis in S. erythraea and provides an efficient approach for boosting erythromycin yield.