Somatostatin has two active forms produced by the alternative cleavage of a single preproprotein: one consisting of 14 amino acids (shown in infobox to right), the other consisting of 28 amino acids.[7][8]
Among the vertebrates, there exist six different somatostatin genes that have been named: SS1, SS2, SS3, SS4, SS5 and SS6.[9]Zebrafish have all six.[9] The six different genes, along with the five different somatostatin receptors, allow somatostatin to possess a large range of functions.[10]
Humans have only one somatostatin gene, SST.[11][12][13]
^Nelson DL, Cox M, Hoskins AA (2021). Lehninger Principles of Biochemistry (Eighth ed.). New York, NY: Macmillan Learning. ISBN978-1-319-22800-2. OCLC1243000176. The binding of somatostatin to its receptor in the pancreas leads to activation of an inhibitory G protein, or Gi, structurally homologous to Gs, that inhibits adenylyl cyclase and lowers [cAMP]. In this way, somatostatin inhibits the secretion of several hormones, including glucagon
^ abLiu Y, Lu D, Zhang Y, Li S, Liu X, Lin H (September 2010). "The evolution of somatostatin in vertebrates". Gene. 463 (1–2): 21–8. doi:10.1016/j.gene.2010.04.016. PMID20472043.