HYDROLYSIS OF LEUCINE-ENKEPHALIN AND ITS ASSOCIATION TO THE K562(S) ERYTHROLEUKEMIC CELL-LINE

Hydrolysis of Leu-enkephalin and association to cells of the radioactive label carried by this peptide have been studied on the K562(S) erythroleukaemic cell subline. Data obtained indicate that in the presence of these cells Leu-enkephalin is rapidly hydrolyzed and that the peptide's radioactive label is partially associated to the cells. Both phenomena are characterized by distinctly diphasic kinetics, and are oppositely modified by cells' stimulated erythroid differentiation. In the presence of proteolysis inhibitors, hydrolysis of Leu-enkephalin and association to cells of its radioactive label are reduced. These data, indicating that enkephalin hydrolysis is a prerequisite for the association of the radiolabel to cells, are consistent with those obtained with other cell lines of different origins and with human mononucleate cells. The modifications induced by differentiation of cells on hydrolysis, association and membrane conductance can be interpreted as an indication of extensive modifications of the membrane structures responsible for the mechanisms controlling those phenomena.