A serine protease inhibitor from hemolymph of green mussel, Perna viridis

Bioactivity guided fractions of cell-free hemolymph of bacterially challenged marine mussel, Perna viridis led to the isolation of a novel quaternary alkaloid 1, which was identified by its spectral data. The isolated molecule 1 has been found to be a potent serine protease inhibitor (SPI) showing IC50 and Ki values of 102.5 and 97.1–104.68 μM, respectively. The Et/Ki value of SPI is 6.3, whereas Et/Km value is 1.04. The Van’t Hoff analysis showed that the value of Ki decreases with increase in temperature, and the binding of the inhibitor is entropically driven.