Purification and Characterization of Caprine Ghrelin and Its Effect on Growth Hormone Release

Abstract Ghrelin, a novel peptide modified by n-octanoic acid at the third serine residue ($ Ser^{3} $), serves as an endogenous ligand for the growth hormone secretagogue receptor (GHS-R) 1a. The octanoyl modification at $ Ser^{3} $ is essential for receptor binding or growth hormone release. Here,...
Ausführliche Beschreibung

Abstract Ghrelin, a novel peptide modified by n-octanoic acid at the third serine residue ($ Ser^{3} $), serves as an endogenous ligand for the growth hormone secretagogue receptor (GHS-R) 1a. The octanoyl modification at $ Ser^{3} $ is essential for receptor binding or growth hormone release. Here, we report the purification of caprine ghrelin and its physiological role in goats. The major form of caprine ghrelin is a 27 amino acid peptide that is octanoylated (C8:0) at $ Ser^{3} $ and lacks $ Gln^{14} $, which is present in rat and human ghrelin. Additionally, we identified various acyl modifications in caprine ghrelin: nonanoic (C9:0), decanoic (10:0), unsaturated octanoic acids (C8:1), and an unidentified fatty acid modification. We observed that differences in acyl modifications affected GHS-R1a activation. In addition, administration of synthetic bovine ghrelin increased plasma growth hormone (GH) levels in goats. Thus, the present study indicates a structural divergence in caprine ghrelin and suggests that ghrelin is involved in GH release in ruminants. Ausführliche Beschreibung