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Parallel bioassay of bombesin and litorin, a bombesin like peptide from the skin of Litoria aurea
No full textThe spectrum of biological activity exhibited by litorin, a bombesin‐like nonapeptide found in extracts of the skin of the Australian leptodactylid frog Litoria aurea was compared with that exhibited by the tetradecapeptide bombesin. Litorin proved to be more potent than bombesin on isolated smooth muscle preparations and on the urinary bladder in situ. However, it was less potent on dog systemic blood pressure and kidney vasculature, activation of the renin‐angiotensin system being slight or lacking. Gastrin release and acid secretion produced by litorin was more rapid in onset but less intense and less sustained than that elicited by bombesin. The same could be observed for pancreatic secretion. Gall bladder contraction stimulated by litorin was probably caused by a double action of the peptide, directly on the bladder smooth muscle, and indirectly by cholecystokinin release. In its effects on the myo‐electric activity of the dog duodenum (inhibition of spikes and increase in frequency of pacesetter potentials leading to the appearance of a sequence of slow and small potentials) litorin possessed approximately 50 to 70% of the activity of bombesin. 1975 British Pharmacological Societ
Parallel bioassay of 39 tachykinins on 11 smooth muscle preparations. Structure and receptor selectivity/affinity relationship
No full textParallel bioassay on smooth muscle preparations demonstrated that: all TKs having a neutral or basic residue at position 7 from the
C-terminus show a clear-cut preference for the NK1 TK receptor, reinforced by the presence of the aromatic doublet Phe-Phe or Phe-Tyr
(aromatic TKs); all aliphatic TKs (Phe-Ile/Val) having an acidic residue at position 7 show a clear-cut preference for NK2/NK3 receptors,
generally without selectivity for a single receptor. However, in aromatic TKs having the same acidic residue, the preference for NK2/NK3
receptors is weakened, with a more or less pronounced co-preference for the NK1 receptor. Amino acid substitutions in the C-terminal
tripeptide may influence receptor affinity
Relative potency of bombesin-like peptides.
No full textThe pharmacological activity of two natural bombesin-like peptides, alytesin and litorin, and 25 related synthetic peptides has been compared to that of bombesin. 2 The minimum length of the amino acid chain required for the first appearance of bombesin-like effects was represented by the C-terminal heptapeptide, and the minimum length for maximal effects by the C-terminal nonapeptide. The latter possessed approximately the same activity as bombesin and may be considered a good substitute. 3 Both the tryptophan and histidine residues seemed to be essential for bombesin-like activity. 4 The C-terminal octapeptide was less active than either bombesin or the C-terminal nonapeptide and its action was more rapid in onset and less sustained. 5 Litorin apparently has an intermediate position between bombesin octapeptide and bombesin nonapeptide in the speed and duration of its effects. The relationship between structure and activity is discussed
Purification and characterization of bioactive peptides from the skin extract of Rana esculenta.
No full textThe peptide fraction extracted by methanol from the skin of Rana esculenta, a species widely distributed in Western Europe, was investigated. The pharmacological activity found in the extract is attributable to the presence of authentic bradykinin, together with a shorter, partially active version of this molecule, des-Arg9-bradykinin. Also the bradykinin fragment 1-7 has been isolated, but it was inactive in our bioassay system. Moreover, a family of hydrophobic peptides has been purified and characterized, which appeared devoid of pharmacological activities when tested on smooth muscle preparations, but were provided with hemolytic activities
Deltorphins: a family of naturally occurring peptides with high affinity and selectivity for delta opioid binding sites.
No full textDeltorphins are endogenous linear heptapeptides, isolated from skin extracts of frogs belonging to the genus Phyllomedusa, that have a higher affinity and selectivity for delta opioid binding sites than any other natural compound known. Two deltorphins with the sequence Tyr-Ala-Phe-Asp(or Glu)-Val-Val-Gly-NH2 have been isolated from skin extracts of Phyllomedusa bicolor. The alanine in position 2 is in the D configuration. These peptides, [D-Ala2]deltorphins I and II, show an even higher affinity for delta receptors than the previously characterized deltorphin, which contains D-methionine as the second amino acid. These peptides show some similarity to another constituent of Phyllomedusa skin, dermorphin, which is highly selective for mu-opioid receptors. These peptides all have the N-terminal sequence Tyr-D-Xaa-Phe, where D-Xaa is either D-alanine or D-methionine. While this structure seems to be capable of activating both mu and delta opioid receptors, differences in the C-terminal regions of these peptides are probably responsible for the observed high receptor selectivity of dermorphin and deltorphin
Structure-activity relationships of the delta-opioid-selective agonists, deltorphins.
No full textDeltorphins are naturally occurring peptides with high affinity and selectivity for δ-opioid receptors. They share with dermorphin, another μ-selective opioid agonist, the same N-terminal tripeptide Tyr-D-Xaa-Phe, where D-Xaa is a D-Ala or a D-Met residue. This common sequence appears to be essential for the best fitting of the peptides to both μ- or δ-opioid sites. We studied the changes in receptor affinity and selectivity and in biological potency of deltorphins due to shortening of the sequence, C-terminal deamidation or single amino acid substitutions. The results support the view that a code addressing the molecule towards δ-opioid sites is expressed in the C-terminal region of these peptides. This addressing domain confers high δ-selectivity to the ligand in the following two ways: (i) increased affinity for δ-sites; (ii) decreased affinity for μ-sites. The sequence of the C-terminal tripeptide appears to be responsible for the high δ-affinity of the molecules. Negatively charged side chains inhibit μ-binding and enhance δ-selectivity
Rohdei-litorin: a new peptide from the skin of Phyllomedusa rohdei.
No full textAbstractThe bombesin-litorin family of peptides is characterized by the common amino acid sequence -Gly-His-X-Met-NH2 at the C-terminus, where X is a hydrophobic or aromatic residue. A new member of this family, rohdei-litorin, has been isolated from amphibian skin and its structure shown to be: Glp-Leu-Trp-Ala-Thr-Gly-His-Phe-Met-NH2. This new peptide displayed a greater affinity than other members of the family for rat urinary bladder receptors. A litorin-like peptide, with high affinity for this kind of receptor, has already been described in mammalian spinal cord and named neuromedin B. Rohdei-litorin shares with neuromedin B the entire C-terminal octrapeptide and may be considered the amphibian counterpart of this mammalian neuropeptide.Rohdei-litorinAmino acid sequencingAmphibian skinNeuromedi
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