Copper-Containing Artificial Polyenzymes as a Clickase for Bioorthogonal Chemistry

Artificial polyenzymes (ArPoly) are tailored combinations of universal protein scaffolds and polymers newly proposed as promising alternatives to natural enzymes to expand the biocatalyst toolbox. The concept of ArPoly has been continuously extended to metal-containing ArPoly to overcome the drawbacks faced by conventional artificial metalloenzymes. Herein, we present a sustainable route to synthesize a novel water-soluble metalloenzyme for copper-catalyzed azide-alkyne cycloadditions in water with remarkable selectivity. In this case, synthetic l-proline monomers were polymerized onto bovine serum albumen in an aqueous medium via copper-mediated "grafting-from" atom-transfer radical polymerization, resulting in protein-polymer-copper conjugates named ArPoly_clickase. The copper in ArPoly_clickase plays pivotal bifunctional roles, not only as the catalyst for polymerization but also as the coordinated active site for alkyne-azide click catalysis. ArPoly_clickase showcases high efficiency, substrate generality, regioselectivity, and ease of product separation for "click chemistry" in water. Notably, ArPoly_clickase displays good biocompatibility without imposing copper toxicity on living cells, which offers the prospect for the upcoming bioorthogonal chemistry.