Bromelains (EC 3.4.4.24) isolated from pineapple fruit and stem have been purified about 18- and 46-folds to homogenity in the same yield of 23%. Molecular weights of fruit- and stem-bromelain were estimated to be 32.5 KDa and 37 KDa by Sephadex G-200, respectively. The enzymes were composed of one subunit. The fruit- and stem-bromelain had their maximum activity at pH 8.0, 70℃ and at pH 7.0, 60℃. Especially the enzymes catalyzed hydrolysis of plant proteins such as ISP (Isolated soybean protein) and wheat gluten with high molecular activity compared to animal proteins. The enzymes were competitively inhibited by sulfhydryl reagent; K_i values of fruit- and stem-bromelain for pCMB (p-chloromercuribenzoate) were 0.18 mM and 0.10 mM. Activities of the enzymes inhibited by pCMB were reversibly restored with increasing concentration of cysteine.