Purification of papain from fresh latex of Carica papaya

In the present study we wish to report a method of crystallizing papain fro m fresh papaya latex which gave higher yields than previously reported. Thi s method does not involve the use of sulphydryl reagents. The papain thus o btained is practically pure and shows a single band when submitted to elect rophoresis on polyacrylamide gel, and is identical to the papain obtained b y other methods. In routine enzymatic assays, specific activity was measure d using Z-gly-pNP and BAEE as substrates. Papain crystallized by this metho d, without the use of high concentrations of salts or thiol-containing subs tances such as cysteine and dithiothreitol, is obtained in the form of a co mplex with natural inhibitors existent in latex which can be removed by dia lysis.