Metalloenzyme efficiency and specificity originate from the cooperative roles between the metal-mediated catalysis at the first coordination sphere and the non-covalent interactions at the secondary coordination sphere. While the structures and functions of metal coordination sites have drawn wide researches, the elucidations of the non-covalent interactions have been less assessed. The enzymatic non-covalent interactions in terms of hydrogen bonding, electrostatic attraction, van der Waals force and hydrophobic interaction are produced from the amino acid residues in the secondary coordination sphere. The primary hurdle that hampers the elucidation of the amino acids in the secondary coordination sphere is their complicated intra- and intermolecular interaction networks that are exceptionally difficult to define. A practical approach to circumvent this challenge is to prepare metalloenzyme mimics that include non-covalent interactions. This approach not only opens an avenue to understand the synergism between the non-covalent interactions and the metal ions, but also contributes to the development of biomimetic catalysts applied in industry, pharmaceutics, biotechnology and even wider areas. To make an overview of the recent progresses in this field, this review discusses the representative mimics which are organized according to the interaction categories. The mimics exemplified here include the ones based on the simple multi-dentate ligands like bipyridine, terpyridine, cyclic amine and porphyrin, and the supramolecular ligands like the functionalized cyclodextrins and calixarenes. Prior to the discussions of mimics, the non-covalent interactions of native metalloenzymes are commented.

Contents
1 Introduction
2 Non-covalent interactions in native metalloenzyme
2.1 Hydrolase
2.2 Oxido-reductase
3 Metalloenzyme models involving non-covalent interactions
3.1 Hydrogen bonding
3.2 Electrostatic interaction
3.3 Hydrophobic sphere
4 Conclusion and outlook