Proglucagon is a protein that is a precursor of glucagon and several other components. It is cleaved from preproglucagon. Proglucagon is generated in the alpha cells of the pancreas and in the intestinal L cells in the distal ileum and colon.

Preproglucagon in humans is encoded by the GCG gene and is composed of 180 amino-acid residues.

Function and Terminology

The “pre-” prefix of preproglucagon indicates that it is composed of proglucagon together with a signal peptide. The signal peptide is a 20 amino acid fragment that signals that the protein needs to be secreted out of the cell. Proglucagon has the “pro-“ prefix because it is a prohormone, which means it is an inactivate precursor that needs to be further modified in order to produce active hormone(s). In particular, proglucagon is cleaved (cut) into different active hormones depending on the organ. Omitting various inactive fragments, preproglucagon is cleaved into the following:

Pancreas

• Signal peptide (1-20)

• Glicentin-related pancreatic polypeptide (GRPP, 21-50)

• Glucagon (53–81)

Gut and Brain

• Signal peptide (1-20)

• Glicentin (21–89)

• Oxyntomodulin (OXY or OXM, 53–89) A further cleavage of Glicentin

• Glucagon-like peptide 1 (GLP-1, 92–128) first seven residues further cleaved

• Glucagon-like peptide 2 (GLP-2, 146–178)

References

Further reading

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