Kinetics studies with fruit bromelain (Ananas comosus) in the presence of cysteine and divalent ions

The kinetics of cysteine and divalent ion modulation viz. Ca2+, Cu2+, Hg2+ 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, Ca2+ inhibited the enzyme noncompetitively, whereas, both K-and V-type activations of bromelain were observed in the presence of 0.5 mM Ca2+ at pH 4.5 and 7.5. Bromelain was inhibited competitively at 0.6 mM Cu2+ ions at pH 3.5, which changed to an uncompetitive inhibition at pH 4.5 and 7.5. An un-competitive inhibition of bromelain catalyzed gelatin hydrolysis was observed in the presence of 0.6 mM Hg2+ at pH 3.5 and 4.5. These findings suggest that divalent ions modulation of fruit bromelain is pH dependent.