Endorphins biological activity

Hormones are intercellular messengers. They are typically (1) steroids (e.g., estrogens, androgens, and mineral corticoids, which control the level of water and salts excreted by the kidney), (2) polypeptides (e.g., insulin and endorphins), and (3) amino acid derivatives (e.g., epinephrine, or adrenaline, and norepinephrine, or noradrenaline). Hormones maintain homeostasis—the balance of biological activities in the body for example, insulin controls the blood glucose level, epinephrine and norepinephrine mediate the response to the external environment, and growth hormone promotes normal healthy growth and development. 

Some of the peptides mentioned are overlapping in the POMC sequence. For example, additional cleavage of ACTH gives rise to a-MSH and corticotropin-like intermediary peptide (CLIP). Proteolytic degradation of p-LPH provides y-LPH and p-endorphin. The latter can be further broken down to yield met-enkephalin, while y-LPH can still give rise to p-MSH (not shown). Due to the numerous derivative products with biological activity that it has, POMC is also known as a polyprotein. Which end product is formed and in what amounts depends on the activity of the proteinases in the ER that catalyze the individual cleavages. 

Numerous HPLC analyses have been carried out on biologically active diastereoisomeric peptides (encephalins, endorphins, hormones) in order to isolate them so that their activity can be studied however, the separation of stereoisomers is not yet common in the field of food science. 

The endorphins are a group of naturally occurring neuroproteins that act in a manner similar to morphine to control pain. Research has shown that the biologically active part of the endorphin molecule is a simple pentapeptide called an enkephalin, with the structure Tyr-Gly-Gly-Phe-Met. Draw the complete structure of this enkephalin. 

Many biologically active secreted peptides are also amidated at their carboxyl terminal, and acetylated at their amino-terminal. The consequences of these modifications are (a) to reduce the susceptibility of these peptides to degradative actions of extracellular aminopeptidases and carboxypeptidases after their secretion and (b) to influence the biological activity of the peptides. Corticotropin-releasing factor, gastrin, cholecystokinin and vasopressin require the C-terminal amide for full activity [54—56]. Acetylation of the N-terminus of a-MSH is necessary for activity, whereas acetylation of /3-endorphin inhibits its opioid activity [57], The enzymes responsible for acetylation have been identified from bovine and rat intermediate lobes [57] and enzymes with a-amidation activity have been reported in preparations of pituitary secretory granules [54,55]. 

Pro-opiomelanocortin. Proopiocortin ACTH-8 lipotropin common precursor precursor to ACTH -LPH-5-endorphin 3lK precursor POMC. A precursor protein oI mol wt about 30,000, synthesized in Che hypothalamus, pituitary gland, brain, and several peripheral tissues that incorporates the amino acid sequences of the pituitary hormones ACTH and (3-lipotropin. These two hormones, in turn, contain biologically active component peptides a-MSH,... 

ACTH is derived from a large polypeptide precursor, proopiomelanocortin (POMC) that also includes in its amino acid sequence both MSH and the related opiate -lipotropin (y3-LPH), the latter giving rise to the biologically active )3-endorphin (Mains and Eipper, 1980). POMC, a 31 kDa polypeptide, is synthesized in the anterior and intermediate lobes of the pituitary gland, which is the most important source of this prohormone. Other notable sources of POMC synthesis in the brain include the amygdala and the arcuate nucleus of the hypothalamus (Watson and Akil, 1980 Civelli et al., 1982). In addition, the structure of the POMC molecule, the POMC gene and the mRNA sequence for POMC have been elucidated (Roberts... 

The cells in the pars intermedia of the rat pituitary produce a series of biologically active peptides, i.e., a-melanocyte-stimulating hormone, CLIP, p-endorphin, P-hpotropin, and y-MSH-related peptides. The pro-opiomelanocortin-derived peptides, especially a-MSH and P-endorphin, are suggested to be involved in learning and memory (O Dono-... 

Finally, the naturalness of proteins does not necessarily make them safe some of the substances with the most powerful biological activity and potential toxicity are peptides and polypeptides (e.g., endorphins, tetanus toxin) and some proteins are known to cause allergic reaction after ingestion (e.g., milk casein, egg albumin, wheat gluten). 

From proopiocortin are derived two lipotropins, corticotropin, three endorphins and two melanocyte-stimulating hormones All these peptides are derived from the C-terminal half of the proopiocortin molecule and the fate of the A-terminal half is unknown. It is quite possible that it gives rise to a completely different set of biologically active peptides, from which it is apparent that there may be many other biologically active peptides yet to be discovered ... 

So, there s actually a biological basis to the euphoric sensation associated with high-level physical activity, such as the runner s high described by long-distance runners and exercise gurus The euphoria is caused by the body s release of endorphins and enkephalins produced by prolonged exercise or stress on the body. 

The authors favour a mode of opioid action in which an N-dealkylase enzyme is first activated either by an endogenous substrate (such as an enkephalin or endorphin which lack N-alkyl substituents) or an exogenous opioid-receptor complex (the enzyme incidentally N-de-alkylates the opioid). The activated enzyme then acts upon an unknown physiological substrate to yield a product which ultimately produces biological responses typical of opioids. Opioid antagonist-receptor complexes fail to activate the enzyme in this scheme. 

P. occur widely and have many different biological functions. Many are hormones, e.g. Corticotropin, Melanotropin, Oxytodn, Vasopressin, Releasing hormones, Insulin, Glucagon, Gastrin, Secretin, Angiotensin, Bradykinin, Endorphins, Opioid peptides (see entries for each of these). Many microorganisms produce P., often with antibiotic activity (see Peptide antibiotics). Some P. are very toxic, e.g. Phallotoxins (see), Amatoxins (see) and Melittin (see). Very simple P. are... 

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