Emerging [FeFe]-hydrogenases: oxygen protection mechanisms and biotechnological potential

The remarkable diversity of enzymes involved in H 2 metabolism provides unique insights into the molecular strategies evolved by nature to overcome challenges in redox chemistry. Among hydrogenases, [FeFe]-hydrogenases contain the H-cluster, a unique metallocofactor that enables rapid and reversible H 2 conversion at minimal overpotential, making them attractive biocatalysts for future hydrogen technologies. This review highlights how the discovery and characterisation of novel [FeFe]-hydrogenases are reshaping our understanding of H-cluster chemistry, enzyme architecture, and biological function. Recent studies have revealed unexpected diversity of structural and functional features, providing fresh perspectives on long-standing questions surrounding enzyme mechanisms and stability. In particular, O 2 -protected [FeFe]-hydrogenases are revealing new mechanisms of aerobic protection while presenting clear advantages for biotechnological implementation, by removing the need for stringent anaerobic handling and facilitating large-scale production. Together, these discoveries elucidate fundamental principles of biological redox catalysis and expand opportunities for sustainable hydrogen biotechnologies.