Improving the System Performance of the Asymmetric Biosynthesis of d-Pantoic Acid by Using Artificially Self-Assembled Enzymes in Escherichia coli.

d-Pantoic acid (d-PA) is an important chiral precursor of a broad range of biologically active compounds. The asymmetric synthesis of d-PA through reductase coupling with NADPH regeneration systems is highly promising, but the process is restricted by expensive cofactor consumption and low cofactor recycling frequency. Here, an effective construction of self-assembled ketopantoic acid reductase and glucose dehydrogenase via protein-peptide interaction of PDZ domain and PDZ ligand was established. The self-assembled enzymes exhibited highly ordered two-dimensional threadlike macromolecular structures with improved cofactor regeneration. Furthermore, the bioconversion with whole-cell catalysis showed that the robustness and efficiency of the system with self-assembled enzymes were significantly higher than those of the unassembled enzymes. This study provides a strategy for the effective asymmetric biosynthesis of d-PA with a trace amount of cofactor and shows potential for industrial applications.