Interfacial Engineering Circumvents Activity–Stability Trade-Off in L-Threonine Aldolase for High-Yield L-threo-MTPS

L-Threonine aldolase (LTA) is pivotal for β-hydroxy-α-amino acids (β-HAAs) synthesis but is limited by poor thermostability and activity–stability trade-off. Here, we applied interfacial engineering to Faecalimicrobium dakarense LTA, targeting nonconserved residues at subunit interfaces. The resulting variant M3 (L17F/V129R/L206W) exhibited 1.23-fold higher specific activity and significantly enhanced thermostability (T5060 + 20.5 °C; Tm + 13.1 °C). In a 1 L system, M3 produced the agrochemical precursor L-threo-4-methylsulfonyl-phenylserine in 2.49-fold higher yield than wild-type. Scaling up to 10 L, M3 achieved 95.7% conversion and 84.9% diastereomeric excess (de), with a high space-time yield of 10.5 g·L–1·h–1. Molecular simulations revealed tighter subunit packing, expanded hydrogen-bonding networks, and enhanced rigidity, collectively improving tetramer stability and catalytic performance. This work presents a generalizable interfacial engineering strategy to decouple activity–stability trade-offs in multimeric enzymes, advancing industrial β-HAAs synthesis.