The proteolytic system of pineapple stems revisited: Purification and characterization of multiple catalytically active forms

Eight cysteine peptidases were isolated from A. comosus stems, including a novel protease, by covalent grafting of a specific and reversible thiol-pegylation reagent. Mass spectroscopy and Far-UV CD analyses revealed very close molecular masses and secondary structure contents. Enzymatic activity measurements using different Fluorophore and chromophore substrates as well as protein substrates clearly demonstrated different substate specificities and allowed to clearly distinguish three different proteases populations.135