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Peptide hormones degradation

The receptors are continuously subjected to a process of synthesis and destruction, which achieves a steady state. The concentration of receptors in the cell only reflects the situation of the steady state at that moment. As a consequence of hormone action, the number of receptors per cell drastically diminishes in the hours that follow. This observation has led to the postulation that the receptors undergo a process of destruction, or processing , induced by the hormone. Despite all efforts, receptor processing has not been deciphered. The destruction of receptors implies the existence of a proteolysis process. Nevertheless, signs of proteolysis, in the form of small peptides of degradation originating in the receptor, have not been detected in the cell. Therefore, if there is a process of receptor proteolysis, it has to be very fast and complete (Beato 1989 Edwards et al. 2002 Kassis et al. 1983). [Pg.50]

Hydrophilic hormones and other water-soluble signaling substances have a variety of biosynthetic pathways. Amino acid derivatives arise in special metabolic pathways (see p. 352) or through post-translational modification (see p. 374). Proteohormones, like all proteins, result from translation in the ribosome (see p. 250). Small peptide hormones and neuropeptides, most of which only consist of 3-30 amino acids, are released from precursor proteins by proteolytic degradation. [Pg.382]

Degradation of peptide hormones often starts in the blood plasma or on the vascular walls it is particularly intensive in the kidneys. [Pg.382]

Since peptide hormones and neurotransmitters act as biological switches, evolutionary development has tended to lead to peptides which have a short duration of biological activity at target tissue and which are rapidly degraded In the biological milieu. [Pg.11]

Some proteins are imported into cells from the surrounding medium examples in eukaryotes include low-density lipoprotein (LDL), the iron-carrying protein transferrin, peptide hormones, and circulating proteins destined for degradation. The proteins bind to receptors in invaginations of the membrane called coated pits, which concentrate endocytic receptors in preference to other cell-surface proteins. The pits are coated on their cytosolic side with a lattice of the protein clathrin, which forms closed polyhedral structures (Fig. 27-40). The clathrin lattice grows as more recep-... [Pg.1074]

It should be pointed out, however, that not all hormones dissociate from their receptor in the pH 5.5 environment of the endosome [24], Some hormone-receptor complexes require much lower pH values for dissociation to occur. Although not a peptide hormone, the iron-transport protein transferrin is a peculiar example of this phenomenon and should be pointed out. In this case, at the neutral pH of the extracellular fluid transferrin containing bound iron binds to its cell surface receptor and is internalized. In the low pH environment of the endosome, iron becomes dissociated from transferrin, but transferrin remains bound to its receptor. The transferrin receptor, with bound transferrin, is then recycled to the cell surface. With iron no longer bound to the transferrin, the transferrin readily dissociates from its receptor at the neutral pH of the extracellular fluid [25,26]. This mechanism provides for an efficient continual uptake of iron into cells. Unlike transferrin, however, in those instances where peptide hormones have been documented not to be dissociated from their receptor in the endosome compartment, the hormone and receptor are delivered to the lysosomes via fusion of the endosomes with lyso-somes, where both hormone and receptor are degraded [24,27]. The continuous degradation of the receptor with each round of RME eventually leads to a decrease in the number of receptors on the cell surface, a phenomenon called down-regulation. [Pg.136]

Polymeric carriers are of particular importance to peptide hormones, because they are generally degraded very fast in the organism. Accordingly, polymer linked peptide hormones have been proposed and investigated by different groups of scientists [e.g. cf. Schuck and Wildi (95)]. [Pg.42]

Pease K, Shen H, Acres GS, Rupnow JH, Dixon JE (1980) Alterations in levels of thyrotrophin releasing hormone and rates of hormone degradation in hypothalamic tissue of the developing rat. J Endocrinol 85(1) 55—61 Queen G, Vivian S, LaBella F (1975) Monolayer cultures of dispersed cells from bovine anterior pituitary responses to synthetic hypophysiotropic peptides. Can J Physiol Pharmacol 53(6) 1094-8... [Pg.358]

Protein and peptide hormones must be administered more frequently if used therapeutically. They cannot be administered by mouth since they would be degraded in the digestive tract. Hence, diabetics must regularly inject with insulin. [Pg.197]


See other pages where Peptide hormones degradation is mentioned: [Pg.126]    [Pg.126]    [Pg.262]    [Pg.282]    [Pg.673]    [Pg.882]    [Pg.272]    [Pg.12]    [Pg.97]    [Pg.603]    [Pg.323]    [Pg.348]    [Pg.270]    [Pg.227]    [Pg.382]    [Pg.757]    [Pg.266]    [Pg.174]    [Pg.628]    [Pg.1745]    [Pg.400]    [Pg.636]    [Pg.657]    [Pg.658]    [Pg.1269]    [Pg.409]    [Pg.300]    [Pg.302]    [Pg.240]    [Pg.128]    [Pg.130]    [Pg.138]    [Pg.139]    [Pg.147]    [Pg.49]    [Pg.197]    [Pg.673]    [Pg.882]    [Pg.91]    [Pg.116]    [Pg.117]    [Pg.372]    [Pg.184]   
See also in sourсe #XX -- [ Pg.382 ]

See also in sourсe #XX -- [ Pg.128 ]




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