The pancreatic stone protein isolated from human calculi (PSP) derives from the immunoreactive protein forms detected in human pancreatic juice (PSP S2-5) through the tryptic cleavage of the Arg-11-Ile-12 bond. Among the eleven amino acids of the PSP S2-5 N-terminal extension Z-E-A-Q-T-E-L-P-Q-A-R, the first residue is an oxoprotine and the fifth, a threonine, bears the single carbohydrate chain of the protein molecules. Variations in the glycan chain composition account for the differences in the Mr of PSP S2-5. The PSP S2-5 forms are very soluble in aqueous solutions between the pH values 5.0-9.0, whereas the proteolysated form is scarcely soluble. © 1989.
De Caro, A. M., Adrich, Z., Fournet, B., Capon, C., Bonicel, J. J., De Caro, J. D., & Rovery, M. (1989). N-terminal sequence extension in the glycosylated forms of human pancreatic stone protein. The 5-oxoproline N-terminal chain is O-glycosylated on the 5th amino acid residue. Biochimica et Biophysica Acta (BBA)/Protein Structure and Molecular, 994(3), 281–284. https://doi.org/10.1016/0167-4838(89)90305-1