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Sensory and Inflammatory Peptide Receptors in Airways
Published in Devendra K. Agrawal, Robert G. Townley, Inflammatory Cells and Mediators in Bronchial Asthma, 2020
Tachykinins produce their effects by interacting with specific surface receptors. Using several tachykinins it is possible to define different patterns of response, suggesting the existence of subtypes of tachykinin receptor. Thus, some tissues were shown to respond most to SP and physalaemin (from amphibia), but not to eledoisin, and these receptors were classified as SP-P receptors. In other tissues, eledoisin (derived from octopus) was more potent than SP and the receptor was therefore termed an SP-E receptor.14 NKA and neuropeptide K are also potent at these receptors, which are now classified as NK2 receptors, in contrast to NK1 receptors, which correspond to SP-P receptors (Figure 1). NKB, by contrast, is more potent at NK3 receptors.15,16 Recently, a fourth type of receptor (NK4) has been proposed based on the unique rank order of potency of newly synthesized tachykinin agonists in guinea pig trachea.17 No endogenous tachykinin which selectively activates this receptor has yet been described. Selective antagonists which discriminate the receptors are not yet available. Recently, the NK2 receptor has been cloned and expressed,18 and the use of cDNA probes for tachykinin receptor subtypes should make it easier to identify which receptor subtype each cell expresses.
Mechanisms Involved in Short-Term Changes in Blood Levels of t-PA
Published in Cornelis Kluft, Tissue-Type Plasminogen Activator (t-PA): Physiological and Clinical Aspects, 1988
No details are available on receptors possibly involved in the release induced by eledoisin, thrombin, or PAF-acether. Thrombin-induced release requires the presence of an intact active site.75,76
Enzymatic Syntheses of Biologically Active Peptides
Published in Willi Kullmann, Enzymatic Peptide Synthesis, 1987
A combination of enzymatic and chemical steps was used for the preparation of a protected eledoisin6-11-hexapeptide (Figure 12).50 However, in contrast to the previously mentioned syntheses of biological peptides or peptide fragments, the authors performed the enzymatic reactions in aqueous-organic biphasic systems. α-Chymotrypsin- and papain-catalyzed syntheses were enhanced both by the use of “preactivated” esterified acyl-group donors and by the precipitation of the resulting products. Furthermore, the extent of synthesis was markedly improved by using a twofold molar excess of the respective amine component. The biphasic systems which were composed of either a papain- or a chymotrypsin-specific buffer and carbon tetrachloride were chosen in order to favor the precipitation of the prospective products. Other work showed that the reaction yields were drastically diminished when a water-immiscible trichloroethylene/petroleum ether mixture or the water-miscible methanol were used in place of carbon tetrachloride. Yet, the degree of synthesis was not solely dependent on the chemical nature of the organic layer but was also affected by the volume ratio of the two phases. In the presence of chymotrypsin the hexapeptide Boc-Ala-Phe-Ile-Gly-Leu-Met-NH2 was obtained in maximum yield from its constituent di- and tetrapeptide (cf. Figure 12) only when carbon tetrachloride formed 60% by volume of the solvent system. Any increase or decrease in this figure resulted in reduced yields. Starting from the same educts, the eledoisin hexapeptide could also be obtained via papain catalysis (Figure 12). Unlike the chymotryptic synthesis, the optimal volume ratio of organic to aqueous phase amounted to 40 to 50% in the presence of papain. An alternative, synthetic route to the eledoisin hexapeptide involved the papain-catalyzed condensation of two tripeptide fragments (cf. Figure 12). In this case, however, the reaction yields remained unchanged when the percentage of organic co-solvent (CCl4) was increased from 10 to 50%.
Neurokinin receptor antagonism: a patent review (2014-present)
Published in Expert Opinion on Therapeutic Patents, 2020
Substance P (SP), hemokinin-1, neurokinin A (NKA), neurokinin B (NKB), neuropeptide K, eledoisin, ranakinin, and kassinin belong to the tachykinin family of peptides which, via the metabotropic neurokinin (NK)-1, NK-2 and NK-3 receptors, exert many physiological actions and are involved in many pathophysiological mechanisms (e.g. cancer, emesis, anxiety, depression, pain, alcohol addiction, inflammation, viral and bacterial infection, pruritus) [1–3].