Xenin

Coatomer subunit alpha
Identifiers
Symbol	COPA
RefSeq	NP_001091868
UniProt	P53621
Other data
Locus	Chr. 1 q23.2

Xenin is a peptide hormone produced by a subpopulation of chromogranin A-positive endocrine cells in the mucous membrane of the duodenum. The peptide has been found in humans, dogs, pigs, rats, and rabbits.

In humans, xenin circulates in the blood plasma.^[1] There is a relationship between peaks of xenin concentration in the plasma and the third phase of the Migrating Motor Complex. For example, infusion of synthetic xenin in fasting volunteers will cause phase III activity. After a meal (the 'postprandial state'), infusion of xenin increases both frequency and the percentage of aborally propagated contractions. In higher concentrations xenin stimulates exocrine pancreatic secretion and inhibits the gastrin-stimulated secretion of acid in dogs. Xenin is also produced in neuroendocrine tumors of the duodenal mucosa.

In vitro, xenin interacts with the neurotensin receptor 1.

Structure and sequence

Xenin is a 25-amino acid polypeptide. The amino acid sequence of xenin is identical to the N-terminal end of cytoplasmic coatomer subunit alpha,^[2] from which xenin can be cleaved by aspartic proteases. Xenin is structurally related to the amphibian peptide xenopsin and to the neuropeptide neurotensin.

Proxenin

Proxenin is the precursor to xenin. It is a 35-amino acid polypeptide. Like xenin, its amino acid sequence exactly matches the N-terminus of coatomer subunit alpha.^[2]

References

1. Feurle GE, Hamscher G, Kusiek R, Meyer HE, Metzger JW (November 1992). "Identification of xenin, a xenopsin-related peptide, in the human gastric mucosa and its effect on exocrine pancreatic secretion". J. Biol. Chem. 267 (31): 22305–9. PMID 1429581.
2. UniProtKB/Swiss-Prot entry P53621 COPA_HUMAN

Further reading

• Feurle GE, Pfeiffer A, Schmidt T, Dominguez-Munoz E, Malfertheiner P, Hamscher G (June 2001). "Phase III of the migrating motor complex: associated with endogenous xenin plasma peaks and induced by exogenous xenin". Neurogastroenterol. Motil. 13 (3): 237–46. doi:10.1046/j.1365-2982.2001.00263.x. PMID 11437986.
• Feurle GE, Anlauf M, Hamscher G, Arnold R, Klöppel G, Weihe E (November 2002). "Xenin-immunoreactive cells and extractable xenin in neuroendocrine tumors of duodenal origin". Gastroenterology. 123 (5): 1616–26. doi:10.1053/gast.2002.36590. PMID 12404236.
• Feurle GE, Ikonomu S, Partoulas G, Stoschus B, Hamscher G (March 2003). "Xenin plasma concentrations during modified sham feeding and during meals of different composition demonstrated by radioimmunoassay and chromatography". Regul. Pept. 111 (1-3): 153–9. doi:10.1016/s0167-0115(02)00281-1. PMID 12609763.
• Taylor AI, Irwin N, McKillop AM, Patterson S, Flatt PR, Gault VA (October 2010). "Evaluation of the degradation and metabolic effects of the gut peptide xenin on insulin secretion, glycaemic control and satiety". J. Endocrinol. 207 (1): 87–93. doi:10.1677/JOE-10-0085. PMID 20631047.
• Leckstrom A, Kim ER, Wong D, Mizuno TM (January 2009). "Xenin, a gastrointestinal peptide, regulates feeding independent of the melanocortin signaling pathway". Diabetes. 58 (1): 87–94. doi:10.2337/db08-0260. PMC 2606897. PMID 18984739.