Peptide synthesis in aqueous–organic biphasic systems catalyzed by a protease isolated from Morrenia brachystephana (Asclepiadaceae)

A new cysteine protease, morrenain b II, isolated from the latex of a South American climbing plant, Morrenia brachystephana Griseb. (Asclepiadaceae), was found to be stable in aqueous–organic biphasic systems. In this work, we have investigated the ability of morrenain b II to perform peptide synthesis using Phe.OMe and Asp as substrates; Cys as activator; 0.1 M Tris–HCl buffer pH 8.5 and chloroform as reaction media. The reaction products were separated by RP-HPLC and identified by TLC, H-NMR and EI-MS. Morrenain b II showed high specificity towards bonds between Cys and Phe.OMe amino acids. A significant amount of the cystine–Phe.OMe peptide was produced within 1 h. These preliminary results were compared with papain under the same conditions.