The major proglucagon fragment: An abundant islet protein and secretory product

Discovery, characterization, and clinical development of the glucagon-like peptides

“…However, it was also clear that proglucagon was larger than glicentin, and the interest focused on peptides contained within the MPGF representing the remainder of proglucagon (minus glicentin) (34). The early work decoding the anglerfish proglucagon cDNA by Lund and Habener (3) followed by elucidation of the hamster proglucagon cDNA by Graeme Bell (9) supported a hypothesis that cleavage of MPGF might result in liberation of the GLPs.…”

The Physiology of Glucagon-like Peptide 1

“…From studies of the biosynthesis of glucagon in the pancreatic islets, however, it was evident that a large molecule (mol wt ϳ10,000), subsequently designated "the major proglucagon fragment" (MPGF) that did not contain the glucagon sequence, was also formed in parallel with glucagon (236). As the structures of glucagon-encoding mRNA and of the glucagon gene were determined (14,15), it became evident that, in mammals, this major fragment of proglucagon contains two glucagon-like sequences, now designated glucagon-like peptides 1 and 2 (GLP-1 and GLP-2, respectively).…”

Conversion of proglucagon in pancreatic alpha cells: the major endproducts are glucagon and a single peptide, the major proglucagon fragment, that contains two glucagon-like sequences.

“…By contrast, the forms that have been attributed to glucagon biosynthesis (1) are completely absent from the protein pattern of D islets. Those forms are proglucagon (18 kDa), a posttranslationally modified proglucagon of slightly reduced electrophoretic mobility, and the conversion product of 10 kDa designated MPGF (1,2). Glucagon itself appears to be covered by heavily labeled insulin chains resulting from stimulated (25 mM glucose) insulin production.…”

“…Accumulation of MPGF as a conversion product of proglucagon in pancreatic islets has been shown by its abundance in the pattern of islet proteins on Coomassie bluestained electrophoresis gels (2). In the fluorograph of islets labeled with [35S]methionine for 2 hr (Fig.…”

“…Conversion of this precursor during pulse-chase experiments resulted in the appearance of a 10-kDa peptide, designated the major proglucagon fragment (MPGF), that did not contain glucagon (2). More recently, the amino acid sequences of three mammalian proglucagons have been deduced from the sequence of cloned DNA complementary to preproglucagon mRNA (3)(4)(5).…”