Isolation and partial characterization of a complex of several (Pro-) endopeptidases from whole porcine pancreatic extract and from purified zymogen granules.
Pancreatic zymogen granules contain exportable proteins at a very high concentration. The mechanism leading to this condensation is unknown. On the other hand, it is known that aqueous extract of pancreatic acetone powder precipitates at low ionic strength and acidic pH. The precipitable fraction is called 'euglobulin' in the literature. We thought that euglobulin could serve as a simplified model to study the condensation of some of the pancreatic exportable proteins. We have compared quantitatively and qualitatively the composition of euglobulins prepared from porcine pancreatic acetone powder and from lysates of purified pancreatic zymogen granules. They were found to be nearly identical, consisting of glycoprotein(s) and/or proteoglycan(s) associated to a proesterase activity, chymotrypsinogens C and D and proelastase. We conclude therefore, that the interactions between the constituents of euglobulin must be specific, since they can occur in the complex protein mixture of the whole organ to a similar extent as in the zymogen granules themselves. We have tried to identify the nature of these specific interactions. We were able to demonstrate that neither the granule membranes, nor the high-molecular-weight proteoglycan present in the granules (Reggio, H.A. and Palade, C.E. (1978) J. Cell. Biol. 77,288-314) were responsible for the observed aggregation. Electrostatic interactions between acidic and basic proteins (Thomson, A. and Denniss, I.S. (1976) Biochim. Biophys. Acta 429, 581-590) were demonstrated between proelastase and chymotrypsinogens C and D. However, the possible roles of the glycoprotein(s) and/or proteoglycan(s) in the condensation process remain unknown.
D000681:Amylases / Q000032:analysis; D000818:Animals; D002268:Carboxypeptidases / Q000032:analysis; D043422:Carboxypeptidases A; D002919:Chymotrypsinogen / Q000032:analysis; D010450:Endopeptidases / Q000032:analysis*; D004792:Enzyme Precursors / Q000032:analysis; D008049:Lipase / Q000032:analysis; D009097:Multienzyme Complexes / Q000032:analysis*; D010179:Pancreas / Q000201:enzymology*; D010196:Pancreatic Elastase / Q000032:analysis; D012712:Serum Globulins / Q000032:analysis; D013552:Swine
D004792:Enzyme Precursors; D009097:Multienzyme Complexes; D012712:Serum Globulins; D002919:Chymotrypsinogen; D008049:Lipase; D000681:Amylases; D002268:Carboxypeptidases; D010450:Endopeptidases; D043422:Carboxypeptidases A; C022443:proelastase; D010196:Pancreatic Elastase