Like any other protein, an enzyme is an amino acid polymer with added cofactors and other post-translational modifications.
In an effort to understand these enzymes, small molecule analogs are created and compared to the data which exists for the proteins.
The structure of some enzymes are very well characterized, however, the function of some component of the active site is poorly understood.
A number of enzymes are an interest since they catalyze a reaction chemist find challenging.
Richard Holm's work on mimics of nitrogenase and creation of iron sulfur clusters.
Thomas Rauchfuss's, Marcetta Darensbourg's and Christopher Pickett's work on Hydrogenase mimics.