Study of immobilized and extracellular aminopeptidases of watermelon

Watermelon cells after permeabilization in Tween 80 were immobilized by glutaraldehyde without any carrier. Cells immobilized by cross-linking demonstrated significantly lower aminopeptidase activities than untreated cells. Pectate and alginate hydrogels were used successfully for immobilization of watermelon cells which retained activities of some aminopeptidases. A simple and rapid procedure for determination of extracellular aminopeptidases was developed using a synthetic substrate. p-Nitroanilides of amino acids were used as substrates for the determination of the extracellular and intracellular enzymatic activities. The culture medium (without cells) was used for the identification and determination of extracellular enzyme activities, whereas intracellular activities were estimated from the cell suspension.