Carboxypeptidase A (CPA) is a zinc metalloenzyme that catalyzes the hydrolysis of the C-terminal amide bond of peptides. The enzyme employs several hydrogen bonding interactions from second sphere amino acids to position substrates and activate a zinc-bound water molecule to act as a nucleophile. Since several cooperative interactions are necessary for catalytic turnover, mimicking the activity of this enzyme is especially challenging. Encapsulation of active sites is a key feature of dendritic catalysts, and the macromolecular backbone can be utilized similarly to protein scaffold in enzymes. The synthesis of dendrimers with catalytic zinc sites has been described including derivatives containing imidazole groups designed to assist in hydrolysis. In addition to cooperative interactions, these dendrimers are designed as """"""""catalytic pumps."""""""" A polarity gradient exists between the exterior and interior of the macromolecular catalysts. Since the core of these molecules is hydrophobic, there is predicted to be an intrinsic driving force for transport of nonpolar substrates (peptides) into the catalytic sites. Following hydrolysis the hydrophilic products are released preventing product inhibition. These studies are expected to provide insight into principles of dendrimers that can be applied to future design catalysts. ? ?
