Transformation of macrolides residues by a novel erythromycin esterase C (Ere C) and safety evaluation of transformed products on Caenorhabditis elegans

In this study, the second enzyme of esterase C family from Enterobacter hormaechei ( Enho -Ere) was identified. The optimum pH and temperature of Enho -Ere was determined at pH 7.0 and 50 °C. At the concentration of 0.8 g/L, 100% erythromycin (Ery), 100 % clarithromycin (Clr), and 50 % roxithromycin (Rox) were transformed by Enho -Ere. Based on transformed products (TPs), a hydrolysis-hydroxyl attack-dehydration reaction process was proposed. Firstly, the lactone ring in macrolides were hydrolyzed. The newly formed hydroxyl from hydrolysis then attacked the unsaturated bond at position C9 to generate the intermediate TPs. Finally, the dehydration happened between the position C6 and C9 to generate the formula isomer of macrolides. In addition, the effects of TPs on Caenorhabditis elegans were evaluated after Enho -Ere treatment. The intracellular ROS level, and the expression of antistress/lifespan-genes of C . elegans all showed significant difference after treatment, indicating that transformation and detoxification of macrolides was both accomplished by Enho -Ere.