The kinetics of cysteine and divalent ion modulation viz. Ca 2+ , Cu
2+, Hg 2+ of fruit bromelain (EC 3.4.22.33) have been investigated in the present study. Kinetic studies revealed that at pH 4.5, cysteine induced V-type activation of bromelain catalyzed gelatin hydrolysis. At pH 3.5, Ca 2+ inhibited the enzyme noncompetitively, whereas, both K-and V-type activations of bromelain were observed in the presence of 0.5 mM Ca 2+ at pH 4.5 and 7.5. Bromelain was inhibited competitively at 0.6 mM Cu 2+ ions at pH 3.5, which changed to an uncompetitive inhibition at pH 4.5 and 7.5. An uncompetitive inhibition of bromelain catalyzed gelatin hydrolysis was observed in the presence of 0.6 mM Hg 2+ at pH 3.5 and 4.5. These findings suggest that divalent ions modulation of fruit bromelain is pH dependent.