Expression and Inhibition Analysis of Recombinant Protease Inhibitor of Solamum Americanum in E. coli

SaPIN2a, the proteinase inhibitor of nightshade (Solanum americanum), has been proposed to regulate proteolysis in phloem development. In this study, we expressed and characterized recombinant SaPIN2a in Escherichia coli. Purified recombinant SaPIN2a (rSaPIN2a) had a strong inhibitory effect on serine proteinase chymotrypsin (IC50 36.1 nmol/L), but its inhibitory activities toward trypsin (IC50 398.6 nmol/L) and especially toward subtilisin (1050 5004 nmol/L) were low. It did not inhibit cysteine proteinase papain and aspartic proteinase cathepsin D. rSaPIN2a was a competitive inhibitor of trypsin, and a noncompetitive inhibitor of chymotrypsin and subtilisin.