SAM-Dependent Fluorinases: Structural Insights, Mechanisms, and Emerging Engineering Strategies

Fluorinated compounds are indispensable in modern pharmaceuticals, agrochemicals, and functional materials, but conventional chemical fluorination typically relies on harsh reaction conditions and toxic reagents. In contrast, S-adenosyl-l-methionine (SAM)-dependent fluorinases catalyze selective biological C–F bond formation under mild and environmentally benign conditions, providing a unique platform for sustainable organofluorine synthesis. In this Review, we summarize recent advances in the discovery, catalytic mechanisms, and engineering of SAM-dependent fluorinases and examine their structural diversity, with particular emphasis on the evolutionary relationships among fluorinases, chlorinases, and hydroxyadenosyl transferase within the DUF62 superfamily. We then discuss the molecular basis of enzymatic fluorination, highlighting the mechanisms of substrate recognition, fluoride desolvation, halide selectivity, and C–F bond formation. Finally, we review recent progress in protein engineering, including strategies to enhance catalytic activity, substrate promiscuity, stability, and selectivity. Together, these advances provide a mechanistic framework for understanding biological fluorination and lay the foundation for developing next-generation fluorinases.