Switching Nitrilase With Enantioselective Hydration Activity for Efficient Synthesis of Chiral 2,2-Dimethylcyclopropanecarboxamide.

Chiral 2,2-dimethylcyclopropanecarboxamides serve as important pharmaceutical intermediates. However, enantioselective synthesis of 2,2-dimethylcyclopropanecarboxamides is difficult due to the unique bond angle and rigid planar structure of the dimethylcyclopropane skeleton. Although nitrile hydratases are attractive for amide biosynthesis, their practical applications are restricted because of narrow substrate spectrum and poor enantioselectivity. The catalytic promiscuity of nitrilases has brought an opportunity to engineer them with specific hydration activity and strict enantioselectivity. Through regulation of the characteristic distances affecting reaction specificity, as well as the key interface structure regions, a nitrilase BaNIT was switched into a novel "nitrile hydratase-like" enzyme with enhanced hydration activity and enantioselectivity toward 2,2-dimethylcyclopropanecarbonitrile. It represented a paradigmatic example for chiral amide synthesis via nitrilase. Compared to the wild type, the proportion of amide synthesized by the mutant increased from 11.2% to 98.8% with enantiomeric ratio (E) value increased from 10.8 to 291. Moreover, in-depth structural-functional analyses provided valuable insights into the molecular mechanisms underlying the enhanced catalytic performance, laying a solid foundation for the rational design of nitrilases with tailored properties for their broader applications.