ISOLATION AND CHARACTERIZATION OF A TUMOR-DERIVED HUMAN PROTEIN RELATED TO CHROMOGRANIN-A AND ITS INVITRO CONVERSION TO HUMAN PANCREASTATIN-48

A protein with pancreastatin‐like immunoreactivity has been isolated and purified from liver metastasis of a patient with insulinoma. NH2‐terminal residue analysis, in conjunction with the use of antibodies that are specific for the C‐terminal amide peptide of porcine pancreastatin, identified this protein as a 186‐amino‐acid protein corresponding to human chromogranin A‐116‐301 (the fragment corresponding to the positions from 116 to 301 of human chromogranin A). Digestion of this protein with trypsin yielded a 48‐amino‐acid peptide with the retention of full pancreastatin activity. Serum from patient with insulinoma contains a peptide specie(s) that comigrates with the 48‐amino‐acid pancreastatin, suggesting that this peptide might be a physiologically important circulation form of pancreastatin in humans. A sensitive radioimmunoassay was established using antibody developed against a synthetic 29‐amino‐acid peptide amide of pancreastatin. Immunocytochemical staining revealed that a major population of human pancreatic islet cells were immunoreactive to the antiserum but with varying intensity of staining. Pancreastatin‐like immunoreactivity was not observed in exocrine acinar cells. Copyright © 1990, Wiley Blackwell. All rights reserved