Abstract: Three new peptides were purified from porcine chromaffin granule lysate, sequenced by N-terminal degradation and identified with mass spectrometry. They were located at chromogranin A 308—324, 308—328 and 308—329; sharing the same N-terninus but with diffferent extends at the C-terninus. The short form of the peptide (CgA 308—324, GN-17) was synthesized and was found to competitively inhibit CK₂ activity at a concentrition as low as 6 μmol/L. The half-maximal inhibition reached at peptide concentration of about 50 μmol/L.

Key words: chromogranin A, active peptide, mass spectrometry, protein kinase CK₂