Human pancreatic proenzymes are activated at different rates in vitro

The rates of activation of procolipase, prophospholipase (proPLA2), chymotrypsinogen, and trypsinogen were studied after incubation of human pancreatic juice with porcine enterokinase in vitro. Under the conditions chosen procolipase was fully activated within 10 min of incubation. Full activation of phospholipase (PLA2) was seen within 15 min, whereas complete activation of chymotrypsin and trypsin was not seen until after 30 to 60 min, respectively. The different proenzymes probably differ in their suitability as substrates for trypsin. A physiologic consequence of a differentiated activation of the pancreatic proenzymes in vivo could be a delayed proteolytic degradation of the lipolytic enzymes in the intestine.