Tripeptide, hormone

Thyrotropin-releasing hormone, or protirelin, is a tripeptide hormone found in the paraventricular nuclei of the hypothalamus as well as in other parts of the brain. TRH is secreted into the portal venous system and stimulates the pituitary to produce thyroid-stimulating hormone (TSH, thyrotropin), which in turn stimulates the thyroid to produce thyroxine (T4) and triiodothyronine (T3). TRH stimulation of thyrotropin is blocked by thyroxine and potentiated by lack of thyroxine. 

In amino acids 3/(C0-Cv) varies between 1-5 and 3-5 Hz. (57, 58) For the proline residue in the tripeptide hormone thyrotropin-releasing factor (TRF, LGlu-His-Pro-NH2) Haar et al. (60) report that 3/(C0-Cy) <0-5 and 37(Ca-Cg) = 3-9 Hz. Using the angular dependence of 3/(C-C) predicted by Barfield et al., (66, 52) Haar and co-workers (60) conclude that the proline residue in TRF is preferentially in the endo conformation in contrast to proline itself. 

TRH Thyrotropin-releasing hormone a tripeptide hormone that is released by the hypothalamus and that acts on the anterior pituitary to stimulate the release of thyroid-stimulating hormone. 

Proteins. The most abundant and physiologically diverse natural biopolymers are proteins, which make up enzymes, hormones, and stmctural material such as hair, skin, and connective tissue. The monomer units of natural proteins, a-amino acids, condense to form dipeptides, tripeptides, polypeptides, and proteins. 

C-Terminal CONH2 Hydrolysis to COOH Luteinizing hormone releasing hormone (Fig. 6.16) [Arg6,D-Trp7,9,MePhe8] substance P-(6-ll)-hexapeptide (6.52, Fig. 6.17) and model tripeptides Klerval (Fig. 6.18) RS-26306 (Fig. 6.19) Pramlintide (Fig. 6.20) Thyrotropin-releasing hormone (Fig. 6.21)... 

The thyrotropin-releasing hormone (TRH) is the hypothalamic tripeptide that releases... 

Skidgel, R.A., Erdos, E.G. (1985) Novel activity of human angiotensin I converting enzyme release of the NH2- and COOH-terminal tripeptides from the luteinizing hormone-releasing hormone. Proc. Natl. Acad. Sci. U. S. A., 82, 1025-1029. 

Thyroid hormones accelerate metabolism. Their release (A) is regulated by the hypophyseal glycoprotein TSH, whose release, in turn, is controlled by the hypothalamic tripeptide TRH. Secretion of TSH declines as the blood level of thyroid hormones rises by means of this negative feedback mechanism, hormone production is automatically adjusted to demand. 

Numerically the largest group of signaling substances, these arise by protein biosynthesis (see p. 382). The smallest peptide hormone, thyroliberin (362 Da), is a tripeptide. Proteohormones can reach masses of more than 20 kDa—e.g., thyrotropin (28 kDa). Similarities in the primary structures of many peptide hormones and proteohormones show that they are related to one another. They probably arose from common predecessors in the course of evolution. 

Proirelin, throtropin-releasing hormone (TRH), synthetic tripeptide, 5-oxo-(pro-his-pro)-ami... 

Hormones related to oxytocin and vasopressin occur in most vertebrates, the compound vasotocin shown in Fig. 30-4 being the most common. Substitution of phenylalanine for isoleucine at position 3 gives arginine vasopressin, the vasopressin found in our bodies. Structure of oxytocin and related hormones82 are also shown in Fig. 30-4. Like somatostatin, vasopressin and oxytocin may also form antiparallel pleated sheet structures with P turns. The structural requirements for hormone activity have been studied intensively. Both the macrocyclic hexapeptide ring and the tripeptide side chains are necessary for maximal activity.83... 

Synthesis of a r >[C(=S)NH] Tripeptide Analogue of Thyrotropin Releasing Hormone pGlm >[C(=S)-NH]His-Pro-NH2J t22l... 

The C-terminal tripeptide tail of oxytocin H-L-Pro-Leu-Gly-NH2 (melanocyte-stimulating hormone release inhibiting factor, MIF or melanostatin) is implicated as having a direct effect on the central nervous system. The ALeu analogue of melanostatin, [ALeu2-MIF] was prepared in view of the earlier work on the active conformation of melanostatin in which a (3-turn was implicated.11771 ALeu was prepared by the N-chlorination/dehydrochlorination reaction and then coupled with Boc-Pro-OH. 

The tripeptide amide L-Pro-L-Leu-Glyamide (melanostatin) is a hypothalamic hormone and an effective therapeutic chelating agent. Its chelating properties have been examined by Kozlowski and his co-workers59 because of thdr interest in proline-containing peptides (Chapter 20.2). With Cu11... 

Protirelin is a synthetic tripeptide that stimulates the hypophyseal secretion of thyrotrophin (thyroid-stimulating hormone, TSH). It is used mainly for diagnostic purposes in dynamic tests of pituitary and hypothalamic... 

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