Molecular cloning and characterization of procirsin, an active aspartic protease precursor from Cirsium vulgare (Asteraceae)

► cDNA encoding an aspartic protease precursor was isolated from Cirsium vulgare flowers. ► The encoded protease (cirsin) shares with cyprosin a striking sequence similarity. ► Recombinant procirsin was active without undergoing any activation process. ► This precursor form displayed the typical proteolytic properties of aspartic proteases. ► Recombinant procirsin also cleaved κ-casein and displayed milk-clotting activity.