Synthesis and Structural/Functional Characterization of Selective M14 Metallocarboxypeptidase Inhibitors Based on Phosphinic Pseudopeptide Scaffold: Implications on the Design of Specific Optical Probes

Metallocarboxypeptidases
(MCPs) of the M14 family are Zn2+-dependent exoproteases
present in almost every tissue
or fluid in mammals. These enzymes perform a large variety of physiological
functions and are involved in several pathologies, such as pancreatic
diseases, inflammation, fibrinolysis, and cancer. Here, we describe
the synthesis and functional/structural characterization of a series
of reversible tight-binding phosphinic pseudopeptide inhibitors that
show high specificity and potency toward these proteases. Characterization
of their inhibitory potential against a large variety of MCPs, combined
with high-resolution crystal structures of three selected candidates
in complex with human carboxypeptidase A (CPA)­1, allowed to decipher
the structural determinants governing selectivity for type-A of the
M14A MCP family. Further, the phosphinic pseudopeptide framework was
exploited to generate an optical probe selectively targeting human
CPAs. The phosphinic pseudopeptides presented here constitute the
first example of chemical probes useful to selectively report on type-A
MCPs activity in complex media.