PR 39 (porcine) acetate is a noncompetitive, reversible and allosteric proteasome inhibitor. PR 39 (porcine) acetate reversibly binds to the α7 subunit of the proteasome and blocks degradation of NF-κB inhibitor IκBα by the ubiquitin-proteasome pathway.

PR-39 (100 nM) blocks TNF-α-induced (1 ng/mL; for 20 minutes) activation of VCAM-1 (2 hours) and ICAM-1 (8 hours) expression in human umbilical vein endothelial cells (HUVEC)[2]. PR-39 (10 μM) does not affect the ability to proliferate of ECV304 cell. PR39 is able to inhibit IκBα degradation without significantly affecting overall protein degradation in cells[2].

PR-39 stimulates angiogenesis, inhibits inflammatory responses and significant reduces myocardial infarct size in mice. PR-39 (10 mg/kg, intravenously; 1 hour before Caerulein of 50μg/kg, ip) blocks IκBα degradation and NF-κB-dependent transcription in the mouse pancreas after induction of acute pancreatitis. PR-39 (1 μg/kg/day; 7-day intraperitoneal infusion) demonstrates significantly small infarct in C57BL/6 mice[2].