Bromelain [EC 3.4.4.24] is the generic name of proteolytic enzymes contained in pineapple plant tissues; those contained its fruit are called fruit-bromelain, and those contained in its stem tissue, stem-bromelain. Stem-bromelain from pineapple (Ananas comosus) of Cheju-Do was purified by 3 successive chromastography: DM-Sephadex C-25. Sephadex G-200 and CM-Sepphadex C-25. Stem-bromelain was purified about 46 folds with and yield of 23%. Molecular weight of the enzyme was estimated 37,000 by Sephadexc G-100 and 33,600 by SDS-electrophoresis. Optimum pH and temperature of the enzyme were pH 8.0 and 60℃. The enzyme had fullactivity in temperature below 50℃ and in pH 6∼8. The enzyme activity was strongly inhibited by Hg^(+2), Fe^(+2) and Fe^(+3). Especially the enzyme activity was inhibited by sulfhydryl reagents such as Hg^(+2) and pCMB. The enzyme was competitively inhibited with pCMB. The enzyme activity inhibited with 1 mM pCMB was considerably restored with increasing concentration of cysteine.