'Salivary peptide P-C' of human pancreatic B-cells shares only partly immunoreactivity with salivary peptide P-C indicating a new B-cell protein which is different from insulin.
Salivary peptide P-C like immunoreactivity, originally isolated from human whole saliva has later been found in the human pancreatic B-cells. In the present work an indirect immunofluorescence technique using monoclonal antibodies against isolated salivary peptide P-C was applied to Bouin fixed pancreas and parotid glands to study the possible identity of the two substances. Positive P-C immunofluorescence was found in the serous cells of parotid glands but not in pancreatic B-cells, suggesting that pancreatic P-C substance is not salivary peptide P-C itself, but a substance sharing the common antigenic site with salivary peptide P-C. To examine this, an indirect immunofluorescence technique using polyclonal P-C antisera pre-absorbed with six kinds of synthetic fragments (1-22, 23-44, 23-29, 30-44, 30-38 and 38-44) of salivary peptide P-C was applied to the human pancreas. The result showed that pancreatic P-C substance was a substance which shares the common antigenic site with the 38-44 amino acid residue of salivary peptide P-C. Western blot analysis using extracts of human pancreata further showed that pancreatic P-C substance is not a precursor of insulin but a protein with molecular weight of 11,500 dalton, indicating the presence of a new protein in the insulin secretory granules of human pancreatic B-cells.
Ito
S
S
First Department of Internal Medicine, Niigata University, Japan.
Suzuki
T
T
Isemura
S
S
Sanada
K
K
Anaguchi
H
H
Shimizu
H
H
Maruyama
T
T
Shibata
A
A
D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000096:biosynthesis; D005455:Fluorescent Antibody Technique; D006801:Humans; D007515:Islets of Langerhans / Q000378:metabolism*; D015394:Molecular Structure; D010446:Peptide Fragments / Q000032:analysis / Q000276:immunology; D010455:Peptides / Q000276:immunology / Q000378:metabolism*; D055232:Proline-Rich Protein Domains; D055273:Salivary Proline-Rich Proteins
D000911:Antibodies, Monoclonal; D010446:Peptide Fragments; D010455:Peptides; D055273:Salivary Proline-Rich Proteins; C524743:salivary peptide P-C