Novel assay for pancreatic cellular damage: 1. Characterization of protein profiles in human pancreatic cytosol and purification and characterization of a pancreatic specific protein

The protein patterns of cytosols from normal human pancreas and pancreatic carcinoma were studied by a two-dimensional separation technique using high-performance liquid chromatography followed by isoelectric focusing on polyacrylamide gels and visualization of the focused proteins by Coomassie Blue staining. Almost identical protein patterns were obtained for 20 different specimens from normal pancreas, whereas quite different protein patterns were found in 12 samples of pancreatic carcinoma. A major protein in normal pancreatic cytosol, not identical to any macromolecule previously tested as a marker for pancreatic function, was selected for further studies. The protein was not found in specimens of pancreatic carcinoma. It was purified by a single step chromatofocusing procedure, focused at pH 6.9, and moved as one single band in sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an apparent molecular weight of 44,500 daltons. Total amino acid analysis revealed a high concentration of glutamic acid, leucine, and lysine. The purified protein had no amylase activity or lipase immunoactivity. It constituted approximately 2% of the total normal pancreatic cytosol protein. Later immunological studies have shown the protein to be highly specific for normal human pancreas, indicating a possible future use as a marker for pancreatic cell damage.