Identification of a procarboxypeptidase A-truncated protease E binary complex in human pancreatic juice

The characterization, in human pancreatic juice, of a binary complex associating procarboxypeptidase A with a 32 kDa inactive glycoprotein (G32) is reported in this paper. Free G32 was isolated after dissociation of the binary complex. N-terminal sequence analysis revealed a complete homology between this protein and human protease E (HPE 1), except for the two strongly hydrophobic N-terminal residues (Val-Val) which are missing in G32. This protein might be a truncated protease E highly analogous to the subunit III of the ruminant procarboxypeptidase A-S6 ternary complex. The analogy with bovine subunit III is further supported by interspecies reassociation experiments showing that bovine procarboxypeptidase A can specifically bind human G32.