Site-directed mutagenesis identified the key active site residues of 2,3-oxidosqualene cyclase HcOSC6 responsible for cucurbitacins biosynthesis in Hemsleya chinensis oleh Xia Li, Xia Li, Geng Chen, Geng Chen, Qing-Qing Gao, Qing-Qing Gao, Chun-Fan Xiang, Chun-Fan Xiang, Cheng-Xiao Yuan, Cheng-Xiao Yuan, Xiao-Ning Li, Yan-Yu Shu, Yan-Yu Shu, Guang-Hui Zhang, Guang-Hui Zhang, Yan-Li Liang, Yan-Li Liang, Sheng-Chao Yang, Chen-Xi Zhai, Yan Zhao, Yan Zhao