Inhibition of Plasma Hyaluronan-Binding Protein Autoactivation by Laccaic Acid

Plasma hyaluronan-binding protein (PHBP) is a serine protease implicated in proteolysis under inflammatory conditions. We identified laccaic acid, a widely used food coloring from scale insects, as a potent inhibitor of the protease in terms of both autoactivation of the PHBP proenzyme (IC₅₀ = 0.35–0.55 μg/ml) and the catalytic activity of the active enzyme (IC₅₀ = 1.1 μg/ml).