Mechanism-Guided Protein Engineering of Paraburkholderia xenovorans Lactamase for the Green Synthesis of 2-(2-Oxopyrrolidin-1-yl)-Butanoic Acid.

The synthesis of tertiary amides is crucial in pharmaceutical manufacturing, but achieving this efficiently through enzymatic methods remains challenging. Here, we describe the screening, evolution, and application of a lactamase for the synthesis of 2-(2-oxopyrrolidin-1-yl)-butanoic acid (2-OYBA) in aqueous phase. Through database mining, we identified a lactamase from Paraburkholderia xenovorans (PxAmpC) with the highest amide synthesis activity in this study at 31.3 U/g. Using protein crystallization, molecular dynamics simulations, and quantum mechanics calculations, we proposed and verified three potential synthesis mechanisms for 2-OYBA. We identified a mechanism for synthesis of 2-OYBA involving adenylation and lactamization, with the carboxyl group in the intermediate 2-2 (INT2-2) acting as a proton shuttle. Guided by this mechanism, rational design efforts enhanced amide synthesis activity by 16.6-fold. The PxAmpC mutants also exhibited a broader substrate scope for amide bond synthesis compared to the wild type. Our findings advance the green synthesis of complex amide compounds.