COMPLETE AMINO-ACID-SEQUENCE OF ANANAIN AND A COMPARISON WITH STEM BROMELAIN AND OTHER PLANT CYSTEINE PROTEASES

The amino acid sequences of ananain (EC3.4.22.31) and stem bromelain ( 3.4.22.32), two cysteine proteases from pineapple stem, are similar ye t ananain and stem bromelain possess distinct specificities towards sy nthetic peptide substrates and different reactivities towards the cyst eine protease inhibitors E-64 and chicken egg white cystatin. We prese nt here the complete amino acid sequence of ananain and compare it wit h the reported sequences of pineapple stem bromelain, papain and chymo papain from papaya and actinidin from kiwifruit. Ananain is comprised of 216 residues with a theoretical mass of 23464 Da. This primary stru cture includes a sequence insert between residues 170 and 174 not pres ent in stem bromelain or papain and a hydrophobic series of amino acid s adjacent to His-157. It is possible that these sequence differences contribute to the different substrate and inhibitor specificities exhi bited by ananain and stem bromelain.