The amino acid sequence of porcine glicentin

Abstract

Glicentin or gut GLI-1 has previously been isolated from porcine small intestine. On the basis of the available chemical data, the molecule was thought to contain 100 amino acid residues. A redetermination of the amino acid composition of the molecule has shown it to contain 69 amino acid residues, and the full sequence has been established. The sequence of glicentin can be outlined as: GRPP 1–30-Lys-Arg-Glucagon 33–61-Lys-Arg-Hexapeptide 64–69 where GRPP 1–30 probably corresponds to the glicentin related pancreatic peptide previously isolated from porcine pancreas. In the pancreas, the two dibasic sequences (Lys 31-Arg 32 and Lys 62-Arg 63) probably represent sites of post-synthetic enzymatic cleavages by analogy with the two dibasic sequences of proinsulin. Glicentin thus fulfills the structural requirements for being all or a part of porcine proglucagon. In the intestine, glicentin could be the precursor of oxyntomodulin, a small molecular weight gut GLI presumably identical to glicentin 33–69, i.e., glucagon extended at the C-terminal end by an octapeptide.