Ghrelin synthesis, maturation and post-translational octanoylation in stomach cells. Preproghelin is first translated from its corresponding gene and then cleaved to produce the proghrelin. Proghrelin is octanoylated on its 3rd amino-acid residue which corresponds to a serine. The octanoylated proghrelin is finally cleaved a 2nd time and secreted in the plasma. Both octanoylated and non-octanoylated ghrelin may co-exist but only the octanoylated form is able to bind to its hypothalamic receptor.