Coenzyme-Mediated Enantioselective Carboligation via Cross-β Amyloid Microphases.

Stereoselective carbon-carbon (C-C) bond formation is a fundamental transformation in metabolism, enabling the generation of chiral molecules essential for life's chemical complexity. While modern enzymes achieve such transformations with the help of cofactor-bound active sites realized via folding of large peptide chains, how primitive peptide folds might have enabled enantioselective C-C bond manipulation in aqueous milieu remains unclear. Here, we report a heptapeptide-based amyloid assembly that catalyzes benzoin-type condensation in water using a thiazolium-based coenzyme inspired by vitamin B1. The leucine-rich hydrophobic nanotubular surface colocalizes coenzyme and substrates, while solvent-exposed imidazole and arginine residues facilitate coenzyme binding and intermediate stabilization. This synergy yields both high reactivity and significant stereocontrol, achieving up to 70 ± 8.8% enantiomeric excess. Mutations of the surface-exposed residues not only modulate but also can reverse the enantioselectivity, highlighting the role of the asymmetric supramolecular microenvironment in influencing chiral outcomes.