The major protein of pancreatic zymogen granule membranes (GP-2) is anchored via covalent bonds to phosphatidylinositol

Biochem Biophys Res Commun. 1988 Jul 29;154(2):818-23. doi: 10.1016/0006-291x(88)90213-6.


GP-2, the major integral protein characteristic of the pancreatic zymogen granule membrane can be released from the membrane by the action of a phosphatidylinositol specific phospholipase C (PI-PLC). In a hydrophobic/hydrophilic phase separation system using the non-ionic detergent Triton X-114, the membrane-bound form of the protein went from the detergent phase into the hydrophilic phase upon action of the phospholipase. PI-PLC solubilization of GP-2 unmasked an antigenic determinant similar to the cross-reacting determinant of the trypanosome variant surface glycoproteins. This determinant being a distinctive feature of the glycan moiety of phosphatidyl-inositol anchored membrane proteins, it established the glycosyl-phosphatidyl-inositol nature of the GP-2 membrane anchor. Since soluble GP-2 is also found in the contents of the granule and is secreted intact into the pancreatic juice, it is likely that one of the mechanisms responsible for its release could be a specific phospholipase. GP-2 is the first glycosyl-phosphatidyl-inositol-anchored protein that is integral to the membrane of an organelle and not located at the surface of the cell.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cytoplasmic Granules / analysis*
  • Enzyme Precursors / analysis*
  • Epitopes / analysis
  • Immunosorbent Techniques
  • Membrane Glycoproteins / metabolism*
  • Membranes / analysis
  • Pancreas / cytology*
  • Pancreas / enzymology
  • Phosphatidylinositols / metabolism*
  • Rats
  • Swine
  • Type C Phospholipases / metabolism


  • Enzyme Precursors
  • Epitopes
  • Membrane Glycoproteins
  • Phosphatidylinositols
  • Type C Phospholipases