Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P01189 (beta-endorphin)
 21,003 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

We studied the binding of [3H]D-Ala2-D-Leu5-enkephalin ([3H]DADLE) and [3H] diprenorphine to crude plasma membrane fraction obtained from the bovine adrenal medulla (bovine adrenal medullary membranes) in order to characterize adrenal medullary opioid receptors. The [3H] diprenorphine binding was the highest in crude plasma membrane-mitochondrial fraction among all subcellular fractions studied. The amount of [3H] diprenorphine bound to bovine adrenal medullary membranes was proportional to the protein concentration. Association kinetics of the [3H] diprenorphine binding to bovine adrenal medullary membranes showed that the maximal binding was achieved following 8 min incubation and that the binding conformed the second-order kinetics. [3H] DADLE and [3H] diprenorphine bound to bovine adrenal medullary membranes with high affinities. The Kd and Bmax for the [3H] DADLE binding were found to be 2.9 nM and 57.5 fmole/mg protein, respectively, while those for the [3H] diprenorphine binding were 0.31 nM and 250 fmole/mg protein, respectively. Displacement studies showed that the [3H] diprenorphine binding was inhibited dose-dependently by levorphanol, dynorphin (1-13), beta-endorphin and DADLE. Levorphanol was at least 1000-fold more potent to inhibit the [3H] diprenorphine binding than dextrorphan, indicating stereospecificity of the [3H] diprenorphine binding. Na+, Li+ and K+ (100 mM) diminished the [3H] DADLE binding and enhanced [3H] diprenorphine binding. Na+ (100 mM) increased the Kd value for the [3H] DADLE binding from 2.9 nM to 14.1 nM. Mn++, Ca++ and Mg++ diminished the [3H] diprenorphine binding. Mn++ (1 mM) increased the Bmax value for the [3H] DADLE binding from 95 fmole/mg protein to 450 fmole/mg protein. These effects of Na+ and Mn++ on the [3H] diprenorphine binding were found to be dose-dependent. [3H] Diprenorphine binding to the digitonin-solubilized opioid receptor was also inhibited dose-dependently by Mn++. These results suggest that bovine adrenal medullary membranes contain high affinity and stereospecific opioid receptors and that the binding of opioids to the bovine adrenal medullary opioid receptors is influenced by cations. Binding study also revealed the presence of opioid receptors in human malignant pheochromocytoma. The Kd and Bmax of the [3H] diprenorphine binding to crude membrane fraction obtained from malignant pheochromocytoma were found to be 0.14 nM and 10.4 fmole/mg protein, respectively.
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PMID:[Characterization of adrenal medullary opioid receptors. I. Binding of opioids to adrenal medullary opioid receptors]. 282 99

Binding of human beta-endorphin (beta h-EP) to bovine adrenal medullary membranes was characterized using [125I]Tyr27-beta h-EP [( 125I]beta h-EP) as a primary ligand. The specific binding of [125I]beta h-EP was time-dependent, saturable and stereospecific. Analysis of a saturation isotherm revealed two apparent classes of specific binding sites with dissociation constants of 2.4 and 34 nM. The extent of maximum inhibition of specific [125I]beta h-EP binding by either levorphanol, morphine, naloxone, dynorphin A (1-13) or D-Ala2-D-Leu5-enkephalin was similar to each other and remained partial (60-70%). Levorphanol eliminated the high affinity component but showed no effect on the low affinity component of [125I]beta h-EP binding. beta h-EP(1-31) displaced completely the [125I]beta h-EP binding. However, beta h-EP(1-23) only partially (approximately 80%) inhibited the [125I]beta h-EP binding. beta h-EP(6-31) showed inhibitory activity on [125I]beta h-EP binding. These results suggest that [125I]beta h-EP binding to bovine adrenal medullary membranes consists of a high affinity opioid-sensitive component and a low affinity non-opioid component. The non-opioid component of [125I]beta h-EP binding may be related to COOH-terminal of the beta h-EP molecule.
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PMID:Opioid and non-opioid binding of beta-endorphin to bovine adrenal medullary membranes. 294 71

Morphine inhibited the adenylate cyclase activity of the crude synaptosomal fraction of the rat caudate nucleus in the presence of BTP, GDP, Gpp(NH)p or ITP. The purine nucleotides themselves had an inhibitory action on the enzyme. Beta-endorphin and Met-enkephalin also inhibited the enzyme in the presence of GTP. The GTP-dependent in inhibitory action of morphine was blocked by naloxone. Various opiates and opioid peptides inhibited the enzyme by up to approximately 20 per cent in the presence of GTP. The relative potency was in higher order of levorphanol greater than beta-endorphin greater than Met-enkephalin greater than morphine greater than pentazocine. Levorphanol was about 50,000 times as potent as its biologically inactive enantiomer, dextrorphan. Morphine enhanced the inhibitory actions of GTP and GTPase-resistant Gpp(NH)p on the adenylate cyclase activity. These results suggest that GTP plays an important role in the regulation of adenylate cyclase activity in the rat caudate nucleus and that the occupation of opiate receptor by agonists inhibits the enzyme through an actual increase in the inhibitory action of GTP, rather than a suppression of the enzymatic degradation of GTP.
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PMID:Inhibition of adenylate cyclase by GTP and its modulation by opiate receptor in rat caudate nucleus. 627 23

The conditions in which Leu(5)-enkephalin inhibition of striatal adenylate cyclase was observed were defined. It was determined that enkephalin inhibition was dependent on GTP. The apparent K(m) for GTP in opiate inhibition was determined to be 0.5 and 2 micrometer when 0.1 mM- and 0.5 mM-ATP were used as substrate. ITP, but not CTP or UTP, could substitute for GTP in the reaction. Though the addition of monovalent cations-Na+, K+, Li+, Cs+, and choline+--stimulated striatal adenylate cyclase activity, enkephalin inhibition of striatal adenylate cyclase did not require Na+ when theophylline was used as the phosphodiesterase inhibitor. Under optimal conditions, i.e., 20 micrometer-GTP and 100 mM-Na+, Leu(5)-enkephalin inhibited the strial adenylate cyclase activity by 23-27%. When the enkephalin regulation of the cyclase activity was further characterized, it was observed that Leu(5)-enkephalin inhibited the rate of the enzymatic reaction. Kinetic analysis revealed that the opioid peptide decreases V (max) values but not the K(m) values for the substrates Mg2+ and Mg-ATP. Agents such as MnCl(2), NaF, and guanyl-5'-ylimido-diphosphate, which directly activated the adenylate cyclase, antagonized the opiate inhibition. Levorphanol and (-)naloxone were more potent than dextrorphan and (+) naloxone in inhibiting adenylate cyclase and in reversing the enkephalin inhibition, respectively. There were differences in the potencies of various opiate peptides in their inhibition of striatal adenylate cyclase activity, with Met5- > Leu(5)-enkephalin > beta-endorphin. The opiate receptor through which the enkephalin inhibition was observed is most likely delta in nature, since in the presence of either Na+ or K+, the magnitude of the alkaloid inhibition was reduced, whereas the peptide inhibition was either potentiated or not affected.
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PMID:Demonstration and characterization of opiate inhibition of the striatal adenylate cyclase. 724 Nov 39