ADP-RIBOSYLATION OF TUFTSIN SUPPRESSES ITS RECEPTOR-BINDING CAPACITY AND PHAGOCYTOSIS-STIMULATING ACTIVITY TO MURINE PERITONEAL-MACROPHAGES

Arginine-specific ADP-ribosyltransferase present in granules of chicke n polymorphonuclear leukocytes (so-called heterophils) is released int o the extracellular space by stimulus of calcium ionophore A23187 or o psonized zymosan (Terashima et al, (1996) J. Biochem, 120, 1209-1215]. In the present work, we examined extracellular targets of the release d transferase and identified tuftsin, a phagocytosis-stimulating tetra peptide derived from leukokinin, as a preferential substrate of the en zyme in chicken plasma, Specific binding of FITC-tuftsin to murine per itoneal macrophages, observed under a fluorescent microscope, was impa ired by ADP-ribosylation of the labelled peptide, Phagocytic assay ana lyzed by flow cytometry revealed that ADP-ribosylation of tuftsin decr eased its phagocytosis-stimulating activity towards the macrophages, T hus, the ADP-ribosylation of tuftsin apparently decreases its biologic al activity and ADP-ribosylation may possibly be involved in inflammat ory processes through alterations in tuftsin activity, (C) 1997 Federa tion of European Biochemical Societies.