Subunit III of bovine procarboxypeptidase A: its relationship to human pancreatic elastase 1

Human alpha 1-antichymotrypsin of pancreatic origin carries blood group determinants

alpha 1-Antichymotrypsin was detected as a minor but normal component of pancreatic juice and found, with the aid of monoclonal antibodies and lectins, to differ from serum alpha 1-antichymotrypsin with respect to its carbohydrate moiety. alpha 1-Antichymotrypsin carries blood group determinants, as is typical for glycoproteins of pancreatic origin.

Carbohydrate structure of human pancreatic elastase 1

Human pancreatic elastase 1 (E1) is a glycoprotein containing two potential N-glycosylation sites, one of which carries a carbohydrate moiety [Wendorf, Geyer, Sziegoleit & Linder (1989) FEBS Lett. 249, 275-278]. In order to study its glycosylation, glycoprotein isolated from post-mortem pancreas tissue of 75 donors was digested with trypsin. Oligosaccharides were liberated from resulting glycopeptides by treatment with peptide-N4-(N-acetyl-beta-glycosaminyl)-asparagine amidase F, radiolabelled by reduction with KB3H4 and separated by h.p.l.c. and gel filtration. Major oligosaccharide alditol fractions, representing 67.8 mol% of total glycans, were characterized by methylation analysis and sequential degradation with exoglycosidases. The results revealed that about two-fifths of the partially truncated, mainly biantennary, complex-type glycans found comprised blood group A, B, Lea (or X), difucosyl A or difucosyl B determinants, which could be assigned to lactosamine antennae linked to Man(alpha 1-3)- residues of the sugar chains.

Studies on the sterol-binding capacity of human pancreatic elastase 1

In previous studies we isolated human pancreatic elastase 1 from intestinal lavage fluids, where it was found to be part of a complex whose major component was cholesterol. The present study involves the isolation and characterization of this elastase 1-sterol complex recovered from feces of healthy subjects and patients whose intestinal microflora were nearly eradicated by antibiotics. Results indicate that elastase 1 essentially is complexed with neutral sterols, i.e., cholesterol, coprostanol, and coprostanone, in a weight ratio of about 1:1.5, corresponding to about 110 molecules of neutral sterols per one elastase 1 molecule. This complex is elutable with water from the solid moiety of the stools. Elastase 1 thus seems to fulfill the important function of maintaining water solubility of neutral sterols at low bile acid concentrations.

Generation of a subunit III-like protein by autolysis of human and porcine proproteinase e in a binary complex with procarboxypeptidase A

Tryptic treatment of human and porcine proproteinase E, procarboxypeptidase A binary complexes gave rise to active proteinase E after removal of an 11-residue N-terminal activation peptide. By contrast, upon treatment of either complex with active proteinase E, not only was the activation peptide released but also the hydrophobic dipeptide Val12-Val13 of the corresponding enzyme. No serine protease activity on specific synthetic peptide substrates could be detected. The structural homology of inactive proteinase E with subunit III of ruminant procarboxypeptidase A was strengthened by the existence of a functional homology since truncated proteinase E still possessed a weakly functional active site. Thus, subunit III-like proteins are generated by proteinase E-catalyzed limited proteolysis of proproteinase E.