Humanpancreatic secretions contain twomajor trypsinogen isoforms, cationic and anionic trypsinogen, normally at a ratio of 2 : 1. Pancreatitis, pancreatic cancer and chronic alcoholism lead to a characteristic reversal of the isoform ratio, and anionic trypsinogen becomes the predominant zymogen secreted. To understand the biochemical conse-quences of these alterations, we recombinantly expressed and purified both human trypsinogens and documented characteristics of autoactivation, autocatalytic degradation and Ca 2+ -dependence
