A study on the directed engineering and multiple transformations of cannabidiolic acid synthase to enhance the expression level of the recombinant enzyme.
To increase the activity of cannabidiolic acid synthase (CBDAS) and its expression levels in yeast, this study focused on the CBDASG183V-N482W mutant. Using computer-aided techniques and literature reviews, four mutation sites were further identified, resulting in the mutant CBDASH114E-S116A-C176Y-G183V-N328Q-N482W. The CBDAS gene was integrated into the Pichia pastoris genome via multiple transformation rounds, and relative enzyme activity was analyzed using high-performance liquid chromatography. The results of the molecular docking analysis revealed factors such as increased intermolecular forces, shorter bond lengths, and an increased number of amino acid-substrate interaction sites, which may have contributed to the enhanced catalytic activity of the mutant. The concentrations of CBDA and CBD produced by the CBDASH114E-S116A-C176Y-G183V-N328Q-N482W mutant were 71.543 ng/mL and 75.163 ng/mL, respectively, which were 11.87% and 11.53% greater than those produced by the CBDASG183V-N482W mutant. The recombinant CBDAS strain obtained after two consecutive transformations of the CBDASH114E-S116A-C176Y-G183V-N328Q-N482W vector presented the highest CBDAS expression levels and CBD and CBDA yields; compared with those obtained after a single transformation, the CBDA and CBD yields increased by 9.77% and 12.65%, respectively. In addition, the tolerance of the recombinant strain to induction culture conditions was analyzed, revealing that the strain could be induced to express the protein at temperatures ranging from 20 to 45 °C and at pH values ranging from 3 to 9, with optimal expression observed at 30 °C and pH 6. These findings provide theoretical and technical support for the production of enzyme preparations for the in vitro-directed biosynthesis of cannabidiol.