Characterization of dipeptidylpeptidase IV (DPP IV) immobilized in Ca alginate beads

Dipeptidylpeptidase IV (DPP IV) (EC 3.4.14.5), purified from goat brain, was immobilized in calcium alginate beads in the presence of bovine serum albumin. The immobilized enzyme retained ∼56% of the original activity and could be used for six successive batch reactions with retention of 25-34% of the initial activity. Immobilized DPP IV hydrolyzed Gly-Pro-4 mβNA maximally at pH 8.5 exhibiting a shift of 0.5 pH unit from that of the soluble enzyme (pH optima 8.0). It showed enhanced stability in acidic as well as alkaline environments in comparison to the free enzyme. The optimal temperature and thermal stabilities were not altered significantly after immobilization. The K′m value (1 mM) for the immobilized enzyme was two-fold higher than for the soluble enzyme.