The glycan moiety of human pancreatic lithostathine. Structure characterization and possible pathophysiological...

Area of Science:

• Glycobiology
• Pancreatic Physiology
• Protein Chemistry

Background:

• Lithostathine (pancreatic stone protein) is a glycoprotein normally in the exocrine pancreas.
• It appears in other tissues pathologically or during regeneration, acting as a growth factor for islet regeneration.
• The role of its glycan moiety in tissue specificity and pathophysiology is largely unknown.

Purpose of the Study:

• To isolate and determine the sequences of oligosaccharide chains from human pancreatic lithostathine.
• To investigate the structural characteristics of lithostathine's glycan structures.
• To understand the potential role of glycosylation in lithostathine's function and properties.

Main Methods:

• Isolation of major oligosaccharide chains from human pancreatic lithostathine.
• Nuclear Magnetic Resonance (NMR) analysis for sequence determination.
• SDS gel electrophoresis and isoelectric focusing for protein polymorphism analysis.

Main Results:

• Eleven different glycoforms were obtained; seven sequences were determined.
• All glycans originated from the same glycosylation site (Thr5) with a common core 2 structure.
• Glycans ranged from 4 to 9 sugar residues, elongated via N-acetyllactosamine units, with some carrying determinant H and sialic acid residues.
• Sialylation appeared to protect a specific peptide bond from hydrolysis, preventing C-terminal polypeptide precipitation.

Conclusions:

• The determined glycan structures provide insight into lithostathine's heterogeneity.
• Glycosylation, particularly sialylation, may play a role in lithostathine's biological functions, including preventing pathological precipitation.
• These findings contribute to understanding lithostathine's role in pancreatic physiology and disease.