Bioactivities and secondary structure of mast cell degranulating (MCD) peptide analogs

Three analogs of Mast Cell Degranulating (MCD) peptide with C-terminal and one analog with N- and C-terminal deletions were synthesized and assayed for histamine-releasing activity in mast cells. Des(20-22)-MCD and des(21)-MCD markedly decreased this activity. In des(16-17,21)-MCD this activity was completely abolished. By contrast, when the C- and N-termini were truncated in des(1-2,20-22)-MCD, the full activity of MCD peptide was restored. The possibility that these analogs trigger or inhibit oxygen radicals from neutrophils was examined in a cell-free system with a chemiluminescence assay. None of the above analogs exhibited inflammatory or anti-inflammatory activity. Changes in biological activities were correlated with structural changes, as seen by circular dichroism (CD) spectroscopy.