A Revised Primary Structure of Neocarzinostatin Using the Combination of Endopeptidase, Carboxypeptidase Y and Fast Atom Bombardment Mass Spectrometry

The amino acid sequence of antitumor protein neocarzinostatin was revised and confirmed on the basis of mass spectrometric studies. Fast atom bombardment mass spectrometric experiments on neocarzinostatin and its tryptic, chymotryptic, staphylococcal protease, and carboxypeptidase Y digested peptides gave the molecular weights of various peptides and, in some cases, partial sequence information. These experiments gave a revised sequence, Glu(105)–Pro(106) to Pro(105)–Glu(106) and Asp(60) to Asn(60). The peptide fragments produced by these endopeptidase cleavage completely covered the full sequence of neocarzinostatin. Thirty-five of the 113 amino acids were determined by the carboxypeptidase Y digestion.