title: A processing enzyme cleaving avian progastrin at post-Phe bonds.
abstract: Neuroendocrine peptides mature partly through endoproteolytic processing of long precursor forms. Best characterised is cleavage at mono- and dibasic residues, but additional sites also exist. Among these is post-Phe cleavage, first suggested to participate in the processing of chicken progastrin. In order to characterise this new mechanism, antibodies recognising the processing products of post-Phe cleavage of chicken progastrin were produced for radioimmunoassay measurements and immunocytochemistry. High concentrations of the carboxyamidated C-terminus and the N-terminus of gastrin-53 were measured in extracts of the antrum. In addition, significant amounts were detected using an assay specific for the N-terminus of gastrin-30 and with another assay for the C-terminus of the corresponding peptide, gastrin-53(1-23), obtained after cleavage at the Phe(23)-Ala(24) bond of gastrin-53. Colocalisation in antral G-cells of the N-termini of gastrin-53 and gastrin-30 and of the C-terminus of gastrin-53(1-23) was confirmed by immunohistochemistry. Finally, we identified the intact N-terminal 1-23 fragment of gastrin-53 complementary to gastrin-30, verifying endoproteolytic cleavage at the Phe(23)-Ala(24) bond. Taken together, the results support the existence of vertebrate endoprotease cleaving hormone precursors at post-Phe sites.
authors.affiliation: Department of Clinical Biochemistry, Rigshospitalet (National University Hospital), Copenhagen, Denmark.
authors.forename: H
authors.initials: H
authors.lastname: Jensen
authors.forename: C
authors.initials: C
authors.lastname: Ørskov
authors.forename: J F
authors.initials: JF
authors.lastname: Rehfeld
authors.forename: A H
authors.initials: AH
authors.lastname: Johnsen
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D000906:Antibodies / Q000276:immunology; D001665:Binding Sites; D002645:Chickens; D002850:Chromatography, Gel; D004064:Digestive System / Q000378:metabolism*; D000939:Epitopes / Q000276:immunology; D005455:Fluorescent Antibody Technique; D005753:Gastric Mucosa / Q000378:metabolism; D005755:Gastrins / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000276:immunology; D011498:Protein Precursors / Q000737:chemistry / Q000276:immunology / Q000378:metabolism*; D011706:Pyloric Antrum / Q000378:metabolism; D011863:Radioimmunoassay; D014020:Tissue Extracts / Q000737:chemistry
chemical_list: D000906:Antibodies; D000939:Epitopes; D005755:Gastrins; D010455:Peptides; D011498:Protein Precursors; D014020:Tissue Extracts; C013706:big gastrin