Activation of porcine pepsinogen A. The stability of two non-covalent activation intermediates at pH 8.5.
Reaction products formed during activation of porcine pepsinogen A at pH 2 were characterized by native agar-gel electrophoresis and by denaturing SDS/PAGE. The results revealed the presence of non-covalent intermediates between prosegment peptides and pepsin. The complexes Leu1p-Leu44p/pepsin and Leu1p-Leu16p/pepsin were isolated (the prosegment residues are characterized by the suffix p; numbering of residues starts again from the N-terminus of pepsin). Relative to mature pepsin, the inherent milk-clotting activities of the intermediates were 3% and 18%, respectively. The intermediates were incubated at pH 8.5 for 20 min at 28 degrees C and the residual proteolytic activities were tested at pH 2. The stabilities at pH 8.5 were between those of pepsinogen and pepsin, Leu1p-Leu44p/pepsin being most stable. The implications of these findings for the conformational changes that occur during the activation of pepsinogen are discussed.
Nielsen
F S
FS
Department of Protein Chemistry, University of Copenhagen, Denmark.
Foltmann
B
B
D000818:Animals; D002851:Chromatography, High Pressure Liquid; D004591:Electrophoresis, Polyacrylamide Gel; D004789:Enzyme Activation; D004795:Enzyme Stability; D006863:Hydrogen-Ion Concentration; D008892:Milk / Q000378:metabolism; D010434:Pepsin A / Q000378:metabolism; D010435:Pepsinogens / Q000378:metabolism*; D013552:Swine
D010435:Pepsinogens; D010434:Pepsin A