In vitro enzymatic synthesis of long-acting therapeutic proteins and peptides.

The site-specific functionalization of therapeutic proteins and peptides represents a significant challenge in modern synthetic chemistry due to the presence of numerous competing nucleophilic residues. Conventional chemical conjugation strategies not only suffer from poor regioselectivity-leading to high product heterogeneity and compromised bioactivity-but also frequently rely on toxic organic solvents and excessive coupling reagents, directly contradicting the principles of green chemistry. In contrast, biocatalysis has become an effective approach for precision bioconjugation. Operating under mild aqueous conditions, enzymatic transformations offer high regio- and chemoselectivity, high atom economy, and minimal environmental footprint. This review focuses on recent advances in the biocatalytic synthesis of functionalized biomacromolecules, covering four highly efficient green modification strategies: enzymatic glycosylation, lipidation, PEGylation, and macrocyclization. The catalytic mechanisms, substrate specificities, and structural engineering of diverse enzyme classes (e.g., transglutaminases, transpeptidases, ligases, and glycosyltransferases) are discussed in the context of generating homogeneous bioconjugates. Furthermore, we analyze current biocatalytic bottlenecks, such as restricted substrate scopes for unnatural polymers, and provide perspectives on how artificial intelligence (AI)-driven generative enzyme design and synthetic biology will further broaden the scope of biocatalytic methods, promoting the sustainable biomanufacturing of long-acting therapeutic proteins and peptides.