Abstract: In this study, the lycopene β-cyclase (LCYb) and lycopene ε-cyclase (LCYe) genes were cloned from maize, and the encoded products were analyzed by bioinformatics methods. After expression in Escherichia coli, the catalytic properties of LCYb and LCYe from maize were explored by color complementation and product analysis experiments. The results of sequence analysis showed that the full-length cDNA of maize LCYb and LCYe were 1 470 and 1 611 bp, respectively, which were more than 90% homologous to those of sorghum and millet. LCYe and LCYb proteins were successfully purified by fusion expression with glutathione thiotransferase tags. The results of color complementation test and high performance liquid chromatography (HPLC) analysis showed that maize LCYb had catalytic activity on β-ring, could cyclize both ends of lycopene to form β-carotene, and had very weak ε-ring catalytic activity, which could form α-carotene through the intermediate γ-carotene. Maize LCYe was also found to able to catalyze both ends of lycopene to form ε-carotene. This study can lay a foundation for exploring the molecular mechanism of the regulation of maize carotenoid.

Key words: maize; lycopene cyclase; gene cloning; color complementation; functional verification