Polypeptide release

The word hormone is derived from the Greek hormaein, meaning to set in motion or to excite. It was used initially to define the activity of secretin [1393-25-5] (1), a gastrointestinal polypeptide released into the blood by the duodenal mucosa to stimulate pancreatic acinar cells to release bicarbonate and water. 

These proteins are called acute phase proteins (or reactants) and include C-reactive protein (CRP, so-named because it reacts with the C polysaccharide of pneumococci), ai-antitrypsin, haptoglobin, aj-acid glycoprotein, and fibrinogen. The elevations of the levels of these proteins vary from as little as 50% to as much as 1000-fold in the case of CRP. Their levels are also usually elevated during chronic inflammatory states and in patients with cancer. These proteins are believed to play a role in the body s response to inflammation. For example, C-reactive protein can stimulate the classic complement pathway, and ai-antitrypsin can neutralize certain proteases released during the acute inflammatory state. CRP is used as a marker of tissue injury, infection, and inflammation, and there is considerable interest in its use as a predictor of certain types of cardiovascular conditions secondary to atherosclerosis. Interleukin-1 (IL-1), a polypeptide released from mononuclear phagocytic cells, is the principal—but not the sole—stimulator of the synthesis of the majority of acute phase reactants by hepatocytes. Additional molecules such as IL-6 are involved, and they as well as IL-1 appear to work at the level of gene transcription. 

Frolova LY, Tsivkovskii RY, Sivolobova GF, Oparina NY, Serpinsky Ol, Blinov VM, Tatkov SI, Kisselev LL (1999) Mutations in the highly conserved GGQ motif of class 1 polypeptide release factors abolish ability of human eRFl to trigger peptidyl-tRNA hydrolysis. RNA 5 1014-1020... 

Figure 8-14 SDS-polyacrylamide gel electrophoresis of human erythrocyte ghosts. (A) From untreated cells. (B) From cells digested externally with chymotrypsin. (C) Inside-out vesicles prepared from cells pretreated with chymotrypsin. (D) The same inside-out vesicles after further treatment with chymotrypsin. (E) Polypeptides released hy the chymotryptic treatment of the inside-out vesides. The peptides are numbered according to the system of Steck232 Hb, hemoglobin. From Luna et al233...

The pancreatic islets consist of four primary cell types alpha (A) cells, which produce glucagon beta (B) cells, which produce insulin delta (D) cells, which produce somatostatin and (F) cells, which produce pancreatic polypeptide. As previously mentioned, this chapter focuses on the functions of insulin and glucagon. The exact physiologic roles of the other pancreatic hormones are not entirely clear. For example, the function of the pancreatic polypeptide released from pancreatic F cells remains to be determined. 

D. V. Freistroffer, M. Kwiatkowski, R.H. Buckingham, and M. Ehrenberg. 2000. The accuracy of codon recognition by polypeptide release factors Proc. Natl. Acad. Sci. USA 97 2046-2051. (PubMed) (Full Text in PMC)... 

Gastric Inhibitory Polypeptide - (G.I.P.) is a 43 amino acid polypeptide released by glucose and fat ingestion. In addition to its insulinotrophic effects in animals and man, G.I.P. inhibits acid secretion in... 

Endorphin is a 31-amino-acid polypeptide released together with ACTH. When introduced into the third ventricle of the brain, it produces dramatic behavioral changes, but when injected systemically, it does not. Thus, the function of circulating 3-endorphin remains unclear. The CNS and gastrointestinal effects of the hormone are probably produced by that secreted locally. Circulating 8-endorphin may act in conjunction with enkephalins released by the adrenal medulla to produce stress analgesia. 

Wt of polypeptide drug, using insulin, calcitonin, trypsin inhibitor and angiotensin II as model polypeptides. Release rates fix>m these systems were controlled by varying the molecular weight (M. Wt.) of the polymers (19), and insulin was used as a model polypeptide drug. 

The names of most enzymes end in ase, and the enzyme s name tells you something about the reaction it catalyzes. For example, carboxypeptidase A catalyzes the hydrolysis of the C-terminal (carboxy-terminal) peptide bond in polypeptides, releasing the terminal amino acid (Section 22.13). 

Insuhn-like growth factor 1 (lGF-1) is a 70-amino-acid single-chain polypeptide released both sys-temicaUy by the liver and locally by muscle and bone (Allori et al. 2008). IGF-1 stimulates cortical and trabecular bone formation (Spencer et al. 1991). Furthermore, IGF-1 administered systemically over 2 weeks stimulated bone formation in rat calvarial defects (Thaller et al. 1993). Despite the potential bone-inducing benefits of IGF-1 administration, its use is limited in bone engineering strategies. 

Termination RFl 36 Promotes polypeptide release at stop codons UAG and UAA... 

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