Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

---

Query: EC:4.6.1.1 (adenylate cyclase)
19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

alpha-Melanotropin (alpha-melanocyte stimulating hormone, alpha-MSH) stimulates tyrosinase activity in Cloudman S91 murine melanoma cells. Three [Nle4, D-Phe7]-substituted alpha-melanotropin analogues, [Nle4, D-Phe7]-alpha-MSH, Ac-[Nle4, D-Phe7]-alpha-MSH4-11-NH2, and Ac-[Nle4, D-Phe7]-alpha-MSH4-10-NH2, are at least 100-fold more effective than alpha-MSH in stimulating melanoma tyrosinase, the rate-limiting enzyme in melanin biosynthesis. These [Nle4, D-Phe7]-substituted melanotropin analogues induce tyrosinase activity in melanoma cells with shorter contact times than required by the native hormone, alpha-MSH. [Nle4, D-Phe7]-substituted melanotropins also induce a prolonged (residual) stimulation of melanoma tyrosinase. Following incubation of melanoma cells in the presence of [Nle4, D-Phe7]-alpha-MSH for 24 h, tyrosinase activity is maintained for up to 6 days in the absence of the melanotropin. The shorter 4-10 and 4-11 fragment analogues also exhibit residual melanotropic activity. The prolonged stimulation of tyrosinase in the absence of the analogues is maintained even though melanoma cells continue to divide about every 24 h. These results suggest that melanoma cells possess spare melanotropin receptors and that [Nle4, D-Phe7]-substituted analogues bind almost irreversibly to these receptors or to some other component of the adenylate cyclase enzyme complex responsible for enhancing tyrosinase activity and melanin production.
...
PMID:Prolonged stimulation of S91 melanoma tyrosinase by [Nle4, D-Phe7]-substituted alpha-melanotropins. 299 67

The efficacy and potency of 14 GH-releasing factor (GRF) analogs, substituted in position 1 to 7, on adenylate cyclase activation in crude homogenates from rat anterior pituitary were related to those of human pancreatic GRF(1-29)-amide and vasoactive intestinal peptide. Among several D-amino acid substitutions, that in position 2 was the only one to yield a super-agonist [with a Kact (concentration required for half-maximal adenylate cyclase activation) 2 times lower than that of GRF(1-29)-NH2]. By contrast, D-isomer substitution in position 1 and 3 was without effect and D-isomer substitution in position 4, 6, or 7 decreased the affinity of the analog. The N-acetylated analog of GRF was as potent and active as the parent peptide, and the identity of the amino acid in position 2 of (N-Ac-Tyr1)-GRF(1-29)-NH2 proved to be determining for enzyme activation, with D-Phe2 and D-Trp2 derivatives acting as partial agonists and the (N-Ac-Tyr1,D-Arg2) analog being an efficient competitive antagonist of GRF(1-29)-NH2. With use of this antagonist, it was possible to demonstrate that GRF and vasoactive intestinal peptide receptors represent distinct entities in the rat anterior pituitary.
...
PMID:Structural requirements for the activation of rat anterior pituitary adenylate cyclase by growth hormone-releasing factor (GRF): discovery of (N-Ac-Tyr1, D-Arg2)-GRF(1-29)-NH2 as a GRF antagonist on membranes. 299 98

The ability of serotonin derivatives to stimulate cAMP accumulation in isolated nerve terminals and lumbar enlargement of the spinal cord of normal rats was compared. The effect of the compounds on the intensity of spinal pain syndrome was also assessed. It has been established that substitutes injected into NH2-group of serotonin in 5-OH position attenuate the ability to stimulate cAMP accumulation in synaptosomes, with the effect more pronounced with substitutes of larger volume. A certain correlation between the ability of serotonin derivatives to stimulate adenylate cyclase in vivo and in vitro, on the one hand, and their analgetic effect, on the other hand, is suggested.
...
PMID:[Mechanism of the suppression of the spinal pain syndrome by serotonin derivatives]. 300 76

The ligand specificity of rat adenohypophyseal vasopressin receptors was directly compared to that of peripheral receptors of the V1 and V2 types. For this purpose a series of 15 recently designed vasopressin antagonists was used. The affinities of these antagonists for rat adenohypophyseal membranes were deduced from the determination of the concentration-dependent inhibition of [3H]vasopressin binding. In parallel experiments the corticotropin (or anti-corticotropin)-releasing activities of the tested peptides were determined on freshly dispersed rat adenohypophyseal cells. All peptides tested which were found to be antagonists of the vasopressor and antidiuretic responses to vasopressin in vivo behaved as antagonists of vasopressin-induced corticotropin release. There was a close correlation between the relative affinities of the analogues tested for binding to adenohypophyseal membranes and their relative potencies in inhibiting vasopressin-induced corticotropin release, indicating that the detected vasopressin-binding sites are the receptors involved in the vasopressin effect on corticotropin secretion. No correlation could be demonstrated between anti-corticotropin-releasing activities and either anti-antidiuretic or antivasopressor potencies of the antagonists tested. A direct comparison of the ligand specificities of adenohypophyseal receptors on the one hand, and V1 (hepatic) and V2 (renal) receptors on the other hand, showed that most of the antagonists discriminated very efficiently between adenohypophyseal and either hepatic or renal receptors. The selectivity index reaches values as high as 260,000 for desGly(NH2)9 [1-(beta-mercapto-beta, beta-cyclopentamethylenepropionic acid), 2-D-O-ethyl-tyrosine, 4-valine] arginine vasopressin. It is concluded that adenohypophyseal receptors represent a novel type of vasopressin receptors. Based on the observation that adenohypophyseal receptors, like hepatic or vascular V1 receptors, do not appear to be coupled to adenylate cyclase, we propose that adenohypophyseal receptors could be designated as V1b receptors as opposed to the V1a receptors previously characterized on liver and blood vessels.
...
PMID:Vasopressin antagonists allow demonstration of a novel type of vasopressin receptor in the rat adenohypophysis. 301

The coronary vasoactivity of N-ethyl-1'-deoxy-1'-(6-amino-9H-purin-9-yl)-beta-D-ribofuranuronamide (NECA, 1) is over 2 orders of magnitude greater than that of adenosine, and the vasoactivity of certain N6-substituted adenosines is as much as 1 order of magnitude greater. Such results suggest that a combination of appropriate modifications at N6 and C-5' might additively augment the agonist potency of adenosine. At low temperatures 1-deoxy-1-(6-chloro-9H-purin-9-yl)-2',3'-O-isopropylidene- beta-D-ribofuranosyl chloride (5), obtained in three steps from inosine, reacts with amines to yield uronamides. The subsequent reaction of such uronamides with amines at elevated temperatures displaces the purine 6-chloro group to yield, after deblocking, N-alkyl(or aryl)-N6-alk(ar)yl-adenosine-5'-uronamides. At the coronary artery A2 receptor the potency of N6-modified analogues of 1 is similar to that of the N6-substituted adenosine, rather than equal to or greater than 1. As agonists in the A2 receptor-mediated stimulation of adenylate cyclase in plasma membranes of PC12 pheochromocytoma cells or human platelets, N6-substituted analogues of 1 are intermediate between the high potency of 1 and the lower potency of the N6-substituted adenosines. At the A1 receptor of rat brain the potency of an N6-substituted analogue of 1 is often greater than that of the corresponding N6-substituted adenosine. At all four receptors, replacing the ethyl group of N-ethyl-N6-3-pentyladenosine-5'-uronamide by larger alkyl groups reduces potency; amides of secondary amines are inactive or have only marginal activity. Analogues of 1 containing a chiral center in the N6 substituent retain the stereoselectivity characteristic of each of the four receptors. Thus, at either A1 or A2 adenosine receptors, adenosine analogues interact with both the N6 and the C-5' receptor regions. However, the effects of N6 and C-5' modifications on potency are less than additive, evidence that the interaction of a substituent with its receptor region influences the interaction of other substituents with their respective receptor regions.
...
PMID:N6-substituted N-alkyladenosine-5'-uronamides: bifunctional ligands having recognition groups for A1 and A2 adenosine receptors. 301 44

We have examined the effects of hGRF on cyclic AMP and glycogen levels in mouse cerebral cortical slices. hGRF-44-NH2 and hGRF-28-OH did not stimulate cyclic AMP formation nor glycogenolysis and did not antagonize the stimulatory effects of VIP on cyclic AMP formation and glycogenolysis. These observations indicate that despite the structural homologies with VIP, hGRF does not interact with VIP receptors coupled to adenylate cyclase in mouse cerebral cortex. This is in contrast with observations in other tissues and species, such as rat and human intestinal epithelial membranes and rat pancreas. We have also compared the effects of hGRF, VIP, PHI and secretin on Growth Hormone (GH) release and cyclic AMP levels in anterior pituitary cells in vitro. VIP and PHI, but not secretin, promote at a high concentration (10(-6) M) a small but significant release of GH. This GH release is accompanied by increases in cyclic AMP levels. The concentration of VIP and PHI required to elicit these effects is high and suggests that VIP and PHI act as low affinity pharmacological analogs of hGRF on hGRF pituitary receptors.
...
PMID:Actions of VIP, hGRF, PHI and secretin: comparative studies in cerebral cortex and adenohypophysis. 301 95

The ability of 30 synthetic GRF(1-29)-NH2 analogs to stimulate adenylate cyclase activity was investigated in membranes from rat adenopituitary, rat liver and rat pancreas. In adenopituitary membranes, GRF and GRF analogs interacted with specific GRF receptors, whereas in liver and pancreatic membranes, they interacted with VIP receptors. The C-terminal moiety of GRF was responsible for GRF receptor recognition as the hybrid analog (His1, D-Ala2)-GRF(1-9), VIP(10-28) stimulated pituitary adenylate cyclase through the occupancy of VIP receptors only. When GRF or VIP receptors were occupied by GRF analogs, the N-terminal part of the ligand appeared critical for adenylate cyclase activation. This was established by testing 30 GRF analogs mono-, bi- or tri-substituted in positions 1 to 10. Major observations included: (a) the characterization of (N-Ac-Tyr1, D-Arg2)-GRF(1-29)-NH2 as an antagonist of GRF-stimulated pituitary adenylate cyclase; (b) the discovery of the (N-Ac-Tyr1, D-Phe2)-, (His1, D-Ala2, D-Ser3, NLeu27)-, and (His1, D-Ala2, D-Thr7, NLeu27)-derivatives of GRF(1-29)-NH2 as specific antagonists of VIP receptors in rat pancreatic membranes; (c) the importance of the free NH2 function of amino acid residue 1 for pancreatic adenylate cyclase activation, and (d) the decreased efficiency of iodinated (Tyr1)-GRF(1-29)-NH2 as opposed to the non iodinated form, in all systems tested.
...
PMID:Comparative structural requirements of thirty GRF analogs for interaction with GRF- and VIP receptors and coupling to adenylate cyclase in rat adenopituitary, liver and pancreas. 301 3

From cross-hybridization studies with cDNAs that code for the alpha subunits of rat brain guanine nucleotide-binding regulatory (G) proteins, we have isolated a gene from yeast Saccharomyces cerevisiae encoding an amino acid sequence that is highly homologous to the alpha subunit of the G protein that mediates inhibition of adenylate cyclase (Gi alpha) from rat brain. The gene, tentatively designated as GPA1, contains a contiguous, single open reading frame of 1416 nucleotides that codes for a protein of 472 amino acids with a calculated Mr of 54,075. The predicted amino acid sequence of the protein encoded by the GPA1 gene (tentatively designated as G protein 1 alpha or GP1 alpha) is remarkably homologous to the amino acid sequence of rat brain Gi alpha and the alpha subunit of the G protein of unknown function (Go alpha); the primary structure of the sites for GTP hydrolysis as well as GTP interaction are nearly identical. The main difference in the molecular sizes of yeast GP1 alpha (472 amino acids) and rat brain Gi alpha (355 amino acids) is due to the presence of a stretch of 110 extra amino acid residues in yeast GP1 alpha, which are inserted near the NH2-terminal one-third of mammalian Gi alpha. From blot-hybridization analysis, the size of the GP1 alpha mRNA was estimated as 1.7 kilobases.
...
PMID:Occurrence in Saccharomyces cerevisiae of a gene homologous to the cDNA coding for the alpha subunit of mammalian G proteins. 303 65

Although prostaglandin E1 is used to dilate the constricted ductus arteriosus in infants with cyanotic heart disease, the mechanism is unknown. To test the hypothesis that the cyclic nucleotides adenosine 3',5'-monophosphate (cAMP) and guanosine 3',5'-monophosphate (cGMP) play a role in relaxation, isolated rings of the ductus arteriosus of fetal lambs were studied. Tension of isometric contraction was measured by force displacement transducers. After contraction with oxygen, a control group was compared with rings in which the stimulus for relaxation was either nitrogen gas, prostaglandin E1 (PGE1), nitroglycerin (NTG), or nitroprusside (NPS). During relaxation, tissue was frozen at 30 seconds and at 1, 2, and 5 minutes and analyzed for cAMP and cGMP. PGE1 (10(-6) mol/L) decreased tension by 33% compared with 70% for nitrogen gas, 81% for NTG (10(-5) mol/L), and 92% for NPS (10(-5) mol/L). The maximal relaxation induced by PGE1 was associated with an 11-fold increase in cAMP; PGE1 had no significant effect on cGMP tissue levels. Nitrogen gas, NTG, and NPS produced similar increases in cAMP, and eight-, 25-, and nine-fold increases in cGMP, respectively. These results suggest that the patency of the ductus arteriosus is dependent on activation of both guanylate cyclase and adenylate cyclase and that the nitrovasodilators may be clinically useful in maintaining patency of the ductus arteriosus.
...
PMID:Role of cyclic nucleotides in relaxation of fetal lamb ductus arteriosus. 303 77

Adenylate cyclase activity was studied in anterior pituitary homogenates from young adult (6 months) and old (20 and 24 months) male rats. Basal, NaF-, GTP-, 5'-guanylimidodiphosphate (Gpp(NH)p)- and forskolin-stimulated activities were similar in the three groups, implying that the stimulatory guanyl nucleotide regulatory binding site (NS) and the catalytical unit were unaffected by aging. Vasoactive intestinal peptide (VIP)-stimulated adenylate cyclase activity was also identical in the three groups. The efficacy (i.e., the maximum effect) of growth hormone-releasing factor [GRF(1-29)-NH2] on adenylate activity was reduced by 45-49% in old and senescent rats with no change in peptide potency (i.e., the concentration required for half-maximal enzyme stimulation). These results suggest that aging induced a selective loss of functional GRF receptors but influenced neither the coupling between receptors, NS and the catalytic unit nor the efficacy of the catalytic unit per se.
...
PMID:Decreased stimulation of adenylate cyclase by growth hormone-releasing factor in the anterior pituitary of old rats. 310 90


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---