Somatostatin analogues (Octreotate
Somatostatin analogues (Octreotate). Somatostatin, a cyclic tetradecapeptide also known as somatotropin release inhibit factor (SRIF), plays a prominent role in the regulation of various biological functions such as the control of growth hormone, glucagon or insulin release from its target cells, acting among others as a neuromodulator and neurotransmitter in the central nervous system. Somatostatins exert their actions after binding to high affinity G protein-coupled receptors including five subtypes. These receptors are expressed in a large variety of human tissues and are noticeably up-regulated in certain types of tumors, especially the sst2. Additionally, synthetic somatostatin analogues radiolabeled with a variety of metallic radionuclides have been used as alternative new routes to diagnosis and therapy of sst-expressing tumors. These derivatives are usually preserving the somatostatin pharmacophore core comprised by Phe-DTrp-Lys-Thr residues while carrying a suitable chelator at the N-terminus which serves as the metal binding site, such as the cyclic octapeptide octreotide (or Sandostatin). The NMR conformational properties of [Tyr3]octreotate (DPhe-Cys-Tyr-DTrp-Lys-Thr-Cys-Thr-COOH; Cys2-Cys7 disulfide bridged) and analogues (Demotate 1), have been determined (PDB: 1YL8 & 1YL9).