Mammalian pancreatic preproglucagon contains three glucagon-related peptides.

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Abstract
C[complementary]DNA clones encoding bovine pancreatic preproglucagon were isolated. A total of 25 putative preproglucagon clones were selected by screening 3100 clones of a fetal bovine pancreas cDNA library with a synthetic oligodeoxynucleotide probe. The probe was a mixture of synthetic 17-base DNA oligomers constructed to correspond to the 6 carboxyl-terminal amino acids (residues 24-29) of mature glucagon. Restriction mapping of 6 of these clones suggested that they represented a single mRNA species. Primary sequence analysis of 1 clone containing a 1200 base-pair DNA insert revealed that it contained an essentially full-length copy of glucagon mRNA. Analysis of the cDNA suggested a protein coding sequence of 540 nucleotides and 5''- and 3''-untranslated regions of 90 and 471 nucleotides, respectively. This cDNA sequence encoded a 20 amino acid signal sequence followed by one for glicentin, a 69-amino acid polypeptide containing an internal glucagon moiety that was found in porcine intestines. Glicentin is followed by 2 additional glucagon-like peptides, each flanked by paired basic amino acids (Lys, Arg) characteristics of prohormone processing. These polypeptide sequences show striking homology with those for glucagon and other members of the glucagon family of peptides.