Glycoprotein 2, Zymogen Granule Membrane (GP2)

The enzyme and zymogen forms of digestive enzymes are stored in secretory zymogen granules (ZGs) in the exocrine pancreas. Since peptide hormones and cholinergic agents enhance release of ZG contents into the apical medium, ZGs constitute an important storage compartment in the regulated secretory pathway. The process of zymogen storage captures large quantities of cellular membranes destined for targeting to the apical plasma membrane. Fukuoka et al. (1991) isolated dog cDNAs encoding GP2, a 75-kD protein that represents the major protein in ZG membranes. They found that GP2 is a GPI (glycosylphosphatidylinositol)-linked membrane protein released from the membrane of mature zymogen granules by an enzymatic mechanism.