Growth hormone secretagogue receptor

ghrelin/growth hormone secretagogue receptorghrelin receptorGHSR
Examorelin (hexarelin). Ghrelin (lenomorelin). GHRP-1. GHRP-3. GHRP-4. GHRP-5. GHRP-6. Ibutamoren (MK-677). Ipamorelin. L-692,585. LY-426410. LY-444711. Macimorelin. Pralmorelin (GHRP-2). Relamorelin. SM-130,686. Tabimorelin. Ulimorelin. A-778,193. PF-5190457.


Growth hormone-releasing peptide 6 (GHRP-6) (developmental code name SKF-110679), also known as growth hormone-releasing hexapeptide, is one of several synthetic met-enkephalin analogues that include unnatural D -amino acids, were developed for their growth hormone-releasing activity and are called growth hormone secretagogues. They lack opioid activity but are potent stimulators of growth hormone (GH) release. These secretagogues are distinct from growth hormone releasing hormone (GHRH) in that they share no sequence relation and derive their function through activation of a completely different receptor.

Protein primary structure

amino acid sequenceprotein sequencesequence
The C-terminal carboxylate group of a polypeptide can also be modified, e.g., Finally, the peptide side chains can also be modified covalently, e.g., Most of the polypeptide modifications listed above occur post-translationally, i.e., after the protein has been synthesized on the ribosome, typically occurring in the endoplasmic reticulum, a subcellular organelle of the eukaryotic cell. Many other chemical reactions (e.g., cyanylation) have been applied to proteins by chemists, although they are not found in biological systems. In addition to those listed above, the most important modification of primary structure is peptide cleavage (by chemical hydrolysis or by proteases).

Growth hormone

human growth hormonegrowth hormonessomatotropin
Growth hormone (GH) or somatotropin, also known as human growth hormone (hGH or HGH) in its human form, is a peptide hormone that stimulates growth, cell reproduction, and cell regeneration in humans and other animals. It is thus important in human development. It is a type of mitogen which is specific only to certain kinds of cells. Growth hormone is a 191-amino acid, single-chain polypeptide that is synthesized, stored and secreted by somatotropic cells within the lateral wings of the anterior pituitary gland. GH is a stress hormone that stimulates production of IGF-1 and raises the concentration of glucose and free fatty acids.

Adrenocorticotropic hormone

corticotropinACTHadrenocorticotrophic hormone
The removal of the signal peptide during translation produces the 241-amino acid polypeptide POMC, which undergoes a series of post-translational modifications such as phosphorylation and glycosylation before it is proteolytically cleaved by endopeptidases to yield various polypeptide fragments with varying physiological activity. These fragments include: In order to regulate the secretion of ACTH, many substances secreted within this axis exhibit slow/intermediate and fast feedback-loop activity. Glucocorticoids secreted from the adrenal cortex work to inhibit CRH secretion by the hypothalamus, which in turn decreases anterior pituitary secretion of ACTH.


cholinergic–dopaminergic reward linkghrelin, the "hunger hormonegrehlin
Unlike the case of many other endogenous peptides, ghrelin is able to cross the blood-brain-barrier, giving exogenously-administered ghrelin unique clinical potential. Ghrelin was discovered after the ghrelin receptor (called growth hormone secretagogue type 1A receptor or GHS-R) was discovered in 1996 and was reported in 1999. The hormone name is based on its role as a growth hormone-releasing peptide, with reference to the Proto-Indo-European root gʰre-, meaning "to grow". The GHRL gene produces mRNA which has four exons. Five products arise: the first is the 117-amino acid preproghrelin. (It is homologous to promotilin; both are members of the motilin family).

Organic compound

syntheticorganicorganic compounds
Further compounds of prime importance in biochemistry are antigens, carbohydrates, enzymes, hormones, lipids and fatty acids, neurotransmitters, nucleic acids, proteins, peptides and amino acids, lectins, vitamins, and fats and oils. Compounds that are prepared by reaction of other compounds are known as "synthetic". They may be either compounds that already are found in plants or animals or those that do not occur naturally. Most polymers (a category that includes all plastics and rubbers), are organic synthetic or semi-synthetic compounds. Many organic compounds—two examples are ethanol and insulin—are manufactured industrially using organisms such as bacteria and yeast.


lactationPRLreceptors, prolactin
Vasoactive intestinal peptide and peptide histidine isoleucine help to regulate prolactin secretion in humans, but the functions of these hormones in birds can be quite different. Prolactin follows diurnal and ovulatory cycles. Prolactin levels peak during REM sleep and in the early morning. Many mammals experience a seasonal cycle. During pregnancy, high circulating concentrations of estrogen and progesterone increase prolactin levels by 10- to 20-fold. Estrogen and progesterone inhibit the stimulatory effects of prolactin on milk production. The abrupt drop of estrogen and progesterone levels following delivery allow prolactin—which temporarily remains high—to induce lactation.


pubescentpubescencesexual development
Neurokinin B (a tachykinin peptide) and kisspeptin (a neuropeptide), both present in KNDy neurons of the hypothalamus, are critical parts of the control system that switches on the release of GnRH at the start of puberty. GnRH (gonadotropin-releasing hormone) is a peptide hormone released from the hypothalamus which stimulates gonadotrope cells of the anterior pituitary. LH (luteinizing hormone) is a larger protein hormone secreted into the general circulation by gonadotrope cells of the anterior pituitary gland. The main target cells of LH are the Leydig cells of testes and the theca cells of the ovaries.


Examples of tripeptides are: Eisenin (pGlu-Gln-Ala-OH) is a peptide with immunological activity that is isolated from the Japanese marine alga, Eisenia bicyclis, which more commonly is known as, Arame. GHK-Cu (glycyl- L -histidyl- L -lysine) is a human copper binding peptide with wound healing and skin remodeling activity, which is used in anti-aging cosmetics and more commonly referred to as copper peptide. Glutathione (γ- L -Glutamyl- L -cysteinylglycine) is an important antioxidant in animal cells. Isoleucine-proline-proline (IPP) found in milk products, acts as an ACE inhibitor.

Amyloid beta

beta amyloidbeta-amyloidβ-amyloid
Early NMR-derived models of a 26-aminoacid polypeptide from amyloid beta (Aβ 10-35) show a collapsed coil structure devoid of significant secondary structure content. However, the most recent (2012) NMR structure of (Aβ 1-40) has significant secondary and tertiary structure. Replica exchange molecular dynamics studies suggested that amyloid beta can indeed populate multiple discrete structural states; more recent studies identified a multiplicity of discrete conformational clusters by statistical analysis.

Macromolecular assembly

macromolecular assembliesBiological Unitmacromolecular structures
The term macromolecular assembly (MA) refers to massive chemical structures such as viruses and non-biologic nanoparticles, cellular organelles and membranes and ribosomes, etc. that are complex mixtures of polypeptide, polynucleotide, polysaccharide or other polymeric macromolecules. They are generally of more than one of these types, and the mixtures are defined spatially (i.e., with regard to their chemical shape), and with regard to their underlying chemical composition and structure.

Cyclic peptide

cyclic peptidescycliccyclic dipeptide
Cyclic peptides are polypeptide chains which contain a circular sequence of bonds. This can be through a connection between the amino and carboxyl ends of the peptide, for example in cyclosporin; a connection between the amino end and a side chain, for example in bacitracin; the carboxyl end and a side chain, for example in colistin; or two side chains or more complicated arrangements, for example in amanitin. Many cyclic peptides have been discovered in nature and many others have been synthesized in the laboratory. Their length ranges from just two amino acid residues to hundreds.


proteolyticprotein degradationpolyprotein
Proteins that are to be targeted to a particular organelle or for secretion have an N-terminal signal peptide that directs the protein to its final destination. This signal peptide is removed by proteolysis after their transport through a membrane. Some proteins and most eukaryotic polypeptide hormones are synthesized as a large precursor polypeptide known as a polyprotein that requires proteolytic cleavage into individual smaller polypeptide chains. The polyprotein pro-opiomelanocortin (POMC) contains many polypeptide hormones. The cleavage pattern of POMC, however, may vary between different tissues, yielding different sets of polypeptide hormones from the same polyprotein.


N-terminalN-amino terminus
The N-terminus (also known as the amino-terminus, NH 2 -terminus, N-terminal end or amine-terminus) is the start of a protein or polypeptide referring to the free amine group (-NH 2 ) located at the end of a polypeptide. Normally the amine group is bonded to another carboxylic group in a protein to make it a chain, but since the end of a protein has only 1 out of 2 areas chained, the free amine group is referred to the N-terminus. By convention, peptide sequences are written N-terminus to C-terminus, left to right in LTR languages.


There are three main classes of biopolymers: polysaccharides, polypeptides, and polynucleotides. In living cells, they may be synthesized by enzyme-mediated processes, such as the formation of DNA catalyzed by DNA polymerase. The synthesis of proteins involves multiple enzyme-mediated processes to transcribe genetic information from the DNA to RNA and subsequently translate that information to synthesize the specified protein from amino acids. The protein may be modified further following translation in order to provide appropriate structure and functioning. There are other biopolymers such as rubber, suberin, melanin and lignin.