Efficient C25-Hydroxylation of Vitamin D₃ Utilizing an Artificial Self-Sufficient Whole-Cell Cytochrome P450 Biocatalyst

Cytochrome P450 enzymes (P450s) are promising candidates for the biosynthesis of 25-hydroxyvitamin D₃ (25(OH)VD₃). However, their industrial application is limited by challenges, such as low stability, inefficient catalysis, and uncoupling reactions. The construction of self-sufficient P450s offers a strategic solution to these limitations, but requires linker optimization to regulate interdomain conformational dynamics. In this study, we integrated whole-cell biocatalyst screening with systematic optimization of reaction conditions, including cosolvents, cell concentrations, and plasmid selection, to enhance catalytic performance. Under optimized conditions, the heme domain Vdh-K1 achieved a 91.6% conversion efficiency and was subsequently selected for chimeric enzyme assembly. By employing local energetic frustration analysis to evaluate protein flexibility and allosteric dynamics, we identified chimeric P450 variants with highly frustrated linkers. The optimal variant, VK1-CYP116B46-L21, exhibited improved thermostability, catalytic activity, and coupling efficiency, achieving a yield of 4.89 mM (1.96 g/L) 25(OH)VD₃ in <i>Escherichia coli</i> whole-cell catalysis─the highest reported yield to date. This work underscores the utility of computational frustration analysis in refining linker dynamics for multidomain enzymes and establishes a scalable, cost-effective framework to advance P450s systems for industrial biosynthesis of high-value compounds.