Allosteric Inhibition of the Neuropeptidase Neurolysin

Neuropeptidases specialize in the hydrolysis of the small bioactive peptides that play a variety of signaling roles in the nervous and endocrine systems. One neuropeptidase, neurolysin, helps control the levels of the dopaminergic circuit modulator neurotensin and is a member of a fold group that includes the antihypertensive target angiotensin converting enzyme. We report the discovery of a potent inhibitor that, unexpectedly, binds away from the enzyme catalytic site. The location of the bound inhibitor suggests it disrupts activity by preventing a hinge-like motion associated with substrate binding and catalysis. In support of this model, the inhibition kinetics are mixed, with both noncompetitive and competitive components, and fluorescence polarization shows directly that the inhibitor reverses a substrate-associated conformational change. This new type of inhibition may have widespread utility in targeting neuropeptidases. Background: Neuropeptidases metabolize regulatory peptides and hormones. Results: A new type of neuropeptidase inhibitor binds away from the catalytic site, is noncompetitive with short peptide substrates, and promotes the open enzyme conformation. Conclusion: The inhibitor restricts a conformational change associated with substrate cleavage. Significance: Inhibitors of this class will allow more specific modulation of neuropeptidases, aiding therapeutic development.