Celandine cells, after permeabilization in Tween 80, were immobilized by crosslinking with glutaraldehyde without any carrier. The cells showed significantly lower aminopeptidase activities than untreated cells. Pectate and alginate hydrogels were successfully used for immobilization of greater celadine cells while retaining the activity of some aminopeptidases. A simple and rapid procedure for determination of extracellular aminopeptidases was developed using synthetic substrates. 4-Nitroanilides of amino acids were used as substrates for the determination of extracellular and intracellular enzymatic activities. The former were determined in culture media (without cells) whereas the latter in a cell suspension culture.