Metalloenzymes are highly specialized proteins that require tightly bound metal ions—such as zinc, iron, copper, manganese, or molybdenum—as integral cofactors for their structural stability and catalytic activity. Constituting approximately one-third of all known enzymes, they are distinct from metal-activated enzymes, which only loosely and reversibly bind versatile metal ions from their surrounding environment to enhance activity.

The Role of Metal Ions in Catalysis In metalloenzymes, metal ions are securely coordinated by specific amino acid residues (like histidine, cysteine, or glutamate) within the enzyme's active site. This allows them to perform highly complex chemical transformations that would otherwise be extremely slow or impossible in biological systems. Their primary catalytic roles include:

• Redox Reaction ...