Glicentin is a 69 amino acid N-terminal peptide derived from proglucagon (PG 1-69) by posttranslational processing in the intestine. Originally thought to represent one of the "enteroglucagon" components, the sequence of glicentin is now known to contain the sequences of glucagon, a carboxyterminal extension (that joined to glucagon would constitute oxyntomodulin-PG 33-69) and an N-terminal extension designated glicentin-related pancreatic peptide. Although originally thought to be ~ 100 amino acids, purification of glicentin from the pig intestine revealed that glicentin was indeed 69 amino acids with a MW of 8128. See The primary structure of porcine glicentin (proglucagon). Regul Pept. 1981 May;2(2):139-50
The structural relationship between GRPP, glucagon, oxyntomodulin and glicentin was confirmed following the cloning of mammalian cDNAs and genes for proglucagon. See Mammalian pancreatic preproglucagon contains three glucagon-related peptides. Proc Natl Acad Sci U S A. 1983 Sep;80(18):5485-9
The available evidence suggests that glicentin is co-secreted from the gut L cell, along with GLP-1 and GLP-2. Glucagon-like peptides GLP-1 and GLP-2, predicted products of the glucagon gene, are secreted separately from pig small intestine but not pancreas. Endocrinology. 1986 Oct;119(4):1467-75. Glicentin and oxyntomodulin have also been identified in the CNS, principally in the hypothalamus and brainstem as shown in Oxyntomodulin and glicentin: brain-gut peptides in the rat. Endocrinology. 1988 Dec;123(6):2782-7 and Distribution of glucagon-like peptide-1 and other preproglucagon-derived peptides in the rat hypothalamus and brainstem. Neuroscience. 1997 Mar;77(1):257-70
The kidney plays a major role in the clearance of glicentin from the circulation, as demonstrated in Renal catabolism of 125I-glicentin. Am J Physiol. 1986 May;250(5 Pt 1):E545-50 and All products of proglucagon are elevated in plasma from uremic patients. J Clin Endocrinol Metab. 1992 Feb;74(2):379-84.
The biological actions of glicentin described to date include stimulation of insulin secretion, inhibition of gastric acid secretion, regulation of gut motility, and stimulation of gut growth. Nevertheless, these same actions may be ascribed to glucagon, GLP-1 and GLP-2, hence it is not clear whether the high doses of glicentin used in these experiments resulted in weak activation of the GLP-1 and GLP-2 receptors. Furthermore, attempts at immunoneutralization of "enteroglucagon" using monoclonal antibodies failed to demonstrate a role for glicentin in gut adaptation after bowel resection. See Enteroglucagon and experimental intestinal carcinogenesis in the rat. Gut. 1987 Jan;28(1):33-9. To date, a separate glicentin receptor has not yet been identified.