Protein Scaffold-Mediated Multi-Enzyme Self-Assembly and Ordered Co-Immobilization of Flavin-Dependent Halogenase-Coenzyme Cycle System for Efficient Biosynthesis of 6-Cl-L-Trp.

Flavin-dependent halogenase (FDH) is highly prized in pharmaceutical and chemical industries for its exceptional capacity to produce halogenated aromatic compounds with precise regioselectivity. This study has devised a multi-enzyme self-assembly strategy to construct an effective and reliable in vitro coenzyme cycling system tailored for FDHs. Initially, tri-enzyme self-assembling nanoclusters (TESNCs) were developed, comprising glucose dehydrogenase (GDH), flavin reductase (FR) and FDH. The TESNCs exhibited enhanced thermal stability and conversion efficiency compared to free triple enzyme mixtures during the conversion of L-Trp to 6-Cl-L-Trp, resulting in a 2.1-fold increase in yield. Subsequently, an ordered co-immobilization of GDH, FR, and FDH was established, further amplifying the stability and catalytic efficiency of the FDH coenzyme cycle system. Compared to the free TESNCs, the immobilized TESNCs demonstrated a 4.2-fold increase in catalytic efficiency in a 5 mL reaction system. This research provides an effective strategy for developing a robust and efficient coenzyme recycling system for FDHs.