Investigation of Subsite Preferences in Aminopeptidase A (EC 3.4.11.7) Led to the Design of the First Highly Potent and Selective Inhibitors of This Enzyme
Abstract
The study of the physiological roles of the membrane-bound zinc-aminopeptidase A (glutamyl aminopeptidase, EC 3.4.11.7) needs the design of efficient and selective inhibitors of this enzyme. An acute exploration of aminopeptidase A active site was performed by a combinatorial approach using (3-amino-2-mercapto-acyl)dipeptides able to fit its S1, S1‘, and S2‘ subsites. This analysis confirmed that the S1 subsite is optimally blocked by a glutamate or isosteric residues and demonstrated that the S1‘ subsite is hydrophobic whereas the S2‘ subsite recognizes preferentially negatively charged residues derived from aspartic acid. The optimization of these structural parameters led to the synthesis of nanomolar and subnanomolar inhibitors of aminopeptidase A such as H3N+CH(CH2CH2SO3-)CH(SH)CO-Ile-(3-COOH)Pro that exhibits a Ki of 0.87 nM. The best compounds were synthesized by a stereochemically controlled route. These first described highly potent inhibitors could allow studies about the role of physiological substrates of APA such as angiotensin II and cholecystokinin CCK8 in the central nervous system.