Human soluble epoxide hydrolase (hsEH) is an enzyme responsible for the inactivation of
bioactive epoxy fatty acids, and its inhibition is emerging as a promising therapeutical
strategy to target hypertension, cardiovascular disease, pain and insulin sensitivity. Here, we
uncover the molecular bases of hsEH inhibition mediated by the endogenous 15-deoxy-Δ12,14-
Prostaglandin J2 (15d-PGJ2). Our data reveal a dual inhibitory mechanism, whereby hsEH can
be inhibited by reversible docking of 15d-PGJ2 in the catalytic pocket, as well as by covalent
locking of the same compound onto cysteine residues C423 and C522, remote to the active
site. Biophysical characterisations allied with in silico investigations indicate that the covalent
modification of the reactive cysteines may be part of a hitherto undiscovered allosteric
regulatory mechanism of the enzyme. This study provides insights into the molecular modes
of inhibition of hsEH epoxy-hydrolytic activity and paves the way for the development of new
allosteric inhibitors