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

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

The distribution of alpha 1-adrenergic receptors in rat liver subcellular fractions was studied using the alpha 1-adrenergic receptor ligand [3H]prazosin. The highest number of [3H]prazosin binding sites was found in a plasma membrane fraction followed by 2 Golgi and a residual microsomal fraction, the numbers of binding sites were 1145, 845, 629 and 223 fmol/mg protein, respectively. When the binding in these fractions was compared with the activity of plasma membrane 'marker' enzymes in the same fractions a relative enrichment of [3H]prazosin binding sites was found in the residual microsomes and one of the Golgi fractions. Photoaffinity labelling with 125I-arylazidoprazosin in combination with SDS-polyacrylamide gel electrophoresis revealed the specific binding to 40 and 23 kDa entities in a Golgi fraction, while in plasma membranes the binders had an apparent molecular mass of 36 and 23 kDa. When [3H]prazosin was injected in vivo into rat portal blood followed by subcellular fractionation of liver, a pattern of an initial rapid decline and thereafter a slow decline of radioactivity was noted in all fractions. Additionally, in the two Golgi fractions a transient accumulation of radioactivity occurred between 5 and 10 min after the injection. The ED50 values for displacement of [3H]prazosin with adrenaline was lowest in the plasma membrane fraction, followed by the residual microsomes and Golgi fractions, the values were 10(-6), 10(-5) and 10(-4) mol/l, respectively. On the basis of lack of correlation between distribution of alpha 1-adrenergic antagonist binding and adenylate cyclase activity, differences in the molecular mass of alpha 1-adrenergic antagonist binders, differences in the kinetics of in vivo binding and accumulation of [3H]prazosin and also differences in agonist affinity between plasma membrane and Golgi fractions, it is concluded that alpha 1-adrenergic receptors are localized to low-density intracellular membranes involved in receptor biosynthesis and endocytosis.
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PMID:Subcellular distribution of alpha 1-adrenergic receptors in rat liver. 303 84

In the mammalian myocardium, an active triglyceride synthesis pathway is operating, (re)esterifying activated fatty acids from endogenous or exogenous sources, with the glycolytically derived three-carbon intermediates dihydroxyacetone-phosphate and glycerol-3-phosphate by the so-called Kennedy pathway. The seven enzymes of triglyceride synthesis are membrane bound and located at the sarcoplasmic reticulum. The first enzyme in the glycerol-3-phosphate pathway, glycerol-3-phosphate acyltransferase, is proposed to be rate limiting for triglyceride formation. This microsomal enzyme is regulated by phosphorylation (inactiycation)-dephosphorylation (activation) coupled to the beta-receptor--adenyl cyclase--protein kinase system. Additional regulatory steps in triglyceride formation are the reactions catalyzed by the microsomal phosphatidic acid phosphatase and diglyceride acyltransferase. Intracellular triglycerides occur as free floating cytosolic droplets, membrane-bound particles and lipid-filled lysosomes. No consensus exists about the metabolically active portion of myocardial triglycerides. Various lipases have been proposed to be involved in endogenous lipolysis: the lysosomal acid, microsomal and soluble neutral triglyceride, intracellular lipoprotein lipases and the microsomal di- and monoglyceridase. It has been acknowledged that the bulk of the intracellular neutral lipase represents the precursor of vascular lipoprotein lipase. The presence of a neutral lipase, as distinct from lipoprotein lipase, in the rat heart was recently advocated. Endogenous lipolysis is a hormone-sensitive process. Hormone-sensitivity may involve direct alteration of enzyme activity by protein phosphorylation-dephosphorylation but is also dependent on the removal rate of product fatty acids, since feedback inhibition is a common property of all lipases in the heart.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Synthesis, storage and degradation of myocardial triglycerides. 331 Oct 5

Thyroid function was studied in 17 unrelated patients with Pendred's syndrome. Fourteen patients had been treated with L-thyroxine, which was withdrawn during the investigation. Eight of the patients had previously had a thyroid resection. Thirteen patients had goiter at the time of study. The serum total thyroxine and serum total triiodothyronine concentrations were normal in 8, of whom 3 had elevated serum TSH concentrations. In the remaining 9 cases the thyroxine levels were below normal with elevated TSH. Serum reverse triiodothyronine concentrations were decreased in 8 out of 11. Median serum thyroglobulin was 973 micrograms/l (range 10.9-3200 micrograms/l) and increased in 13. Three patients had slightly positive thyroglobulin antibodies and one with normal level was thyrodectomized. Thyroid stimulating antibodies as measured by adenylate cyclase stimulation (median 114%, range 85-137%) were slightly increased in 11. When measured as TSH binding inhibiting immunoglobulins none were positive. Thyroid microsomal antibodies were negative in all. All patients with a detectable 131I uptake (n = 15) showed a pathological iodide perchlorate discharge test (median 32%, range 16-46%). These findings indicate an organification defect with impaired hormone synthesis.
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PMID:Thyroid function in patients with Pendred's syndrome. 336 Oct 85

An automated high-performance liquid chromatographic method for the assay of 3',5'-cyclic AMP was developed using octylsilica. Total analysis time was 10.1 min, with cAMP eluting at 3 min. As little as 10 pmol of cyclic AMP could be detected by absorption at 260 nm. Peak height and area were linearly related to cyclic AMP concentration over at least two orders of magnitude. The analytical procedure gave good results in the assay of crude microsomal preparations of adenylate cyclase from both bovine brain and sea urchin eggs. The method was used to demonstrate that sea urchin adenylate cyclase is a Ca2+-activated enzyme.
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PMID:An automated assay for adenylate cyclase using reversed-phase high-performance liquid chromatography. 367 2

A rapid method of preparing plasma membranes from isolated fat cells is described. After homogenization of the cells, various fractions were isolated by differential centrifugation and linear gradients. Ficoll gradients were preferred because total preparation time was under 3 hr. The density of the plasma membranes was 1.14 in sucrose. The plasma membrane fraction was virtually uncontaminated by nuclei but contained 10% of the mitochondrial succinic dehydrogenase activity and 25-30% of the RNA and reduced nicotinamide adenine dinucleotide cytochrome c reductase activity of the microsomal fraction. Part of the RNA and NADH-cytochrome c reductase activity was believed to be native to the plasma membrane or to the attached endoplasmic reticulum membranes demonstrated by electron microscopy. The adenyl cyclase activity of the plasma membrane fraction was five times that of Rodbell's "ghost" preparation and retained sensitivity to epinephrine. The plasma membrane ATPase activity was five times that of the homogenate and microsomal fractions. Electron microscopic evidence suggested contamination of the plasma membrane fraction by other subcellular components to be less than the biochemical data indicated.
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PMID:Preparation and characterization of a plasma membrane fraction from isolated fat cells. 424 33

1. The Gilman (1970) procedure for determining cyclic AMP (adenosine 3':5'-cyclic monophosphate) by saturation analysis gave erroneous results when applied to the analysis of extracts of whole brain or preparations of membrane fragments from brain. 2. The extracts contained a non-diffusible factor, which enhanced the binding of cyclic AMP by the muscle protein fraction. 3. Extracts also contained material which inhibited binding, but net inhibition of binding was only observed when relatively concentrated extracts were analysed. 4. The error introduced by the factors modifying binding could be eliminated by incorporation of unlabelled internal standards in the unknowns. The design adopted enables a statistical estimate to be made of the standard error of a single assay. 5. The modified assay was used to determine bound cyclic AMP and adenylate cyclase activity in cerebral membrane fragments. Five preparations of synaptic membrane fragments contained less than 3.5pmol of cyclic AMP/mg of protein; a microsomal fraction from rat contained 65pmol of cyclic AMP/mg of protein.
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PMID:Determination of adenosine 3':5'-cyclic monophosphate in cerebral tissues by saturation analysis. Assessment of a method using a binding protein from ox muscle. 434 52

Epinephrine modulation of the fatty acyl-CoA desaturase activities in Tetrahymena microsomes, namely the stimulation of delta 9 desaturase activity with a decreased activity of delta 12 desaturase, was markedly inhibited by dexamethasone administered 30 min prior to epinephrine addition. This effect by dexamethasone was dose-dependent. With epinephrine or dexamethasone prior to epinephrine administration, the activities of delta 9-terminal and delta 12-terminal components were found to change in parallel with those of delta 9 and delta 12 desaturase activities respectively. Furthermore, addition of dexamethasone as early as 30 min before epinephrine repressed the epinephrine-mediated stimulation of cyclic AMP production and of adenylate cyclase activity. Therefore, it is suggested that dexamethasone may inhibit the modulation by epinephrine of the terminal component activity, which plays a crucial role in microsomal fatty acyl-CoA desaturase system, through the reduction of cyclic AMP accumulation by decreased responsiveness to epinephrine of Tetrahymena cells.
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PMID:Repression by dexamethasone of epinephrine-induced modulation of the fatty acyl-CoA desaturase system in Tetrahymena microsomes. 608 51

The binding of radiolabeled glucagon to rat brain membranes was investigated. Regional distribution studies indicate higher specific binding of 125I-labeled monoiodoglucagon to olfactory tubercule, hippocampus, anterior pituitary, and amygdala membranes, with somewhat lower binding to membranes from septum, medulla, thalamus, olfactory bulb, and hypothalamus. 125I-labeled glucagon bound to rat brain synaptic plasma membrane fractions with high affinity (KD = 2.24 nM). Specific binding was greater to synaptosomal membrane fractions relative to myelin, mitochondrial nuclear, or microsomal fractions. Inclusion of 0.1 mM GTP in the binding assay reduced the glucagon binding affinity (KD = 44.5 nM). Several neuropeptides and other neuroactive substances tested did not affect binding of labeled glucagon to brain membranes. Three different glucagon analogs inhibited labeled glucagon binding. Synthetic human pancreatic growth hormone-releasing factor, hpGRF-44, also inhibited binding, although the concentration required for half-maximal displacement was 100-fold higher than for native glucagon. Addition of glucagon to brain membranes resulted in approximately equal to 3-fold maximal activation of adenylate cyclase over basal levels. Glucagon at a concentration of 4.74 nM was required for half-maximal activation of pituitary membrane adenylate cyclase. These findings provide evidence for rat brain binding sites that respond to the pancreatic form of glucagon and can transduce this binding into the activation of adenylate cyclase.
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PMID:Identification of glucagon receptors in rat brain. 608 21

Cytochemical and biochemical characteristics of the surface membrane components of avian dystrophic muscle were examined. A Mg2+- or Ca2+-activated ("basic") adenosine triphosphate (ATPase) was localized cytochemically in fixed, intact dystrophic muscle slices in a medium containing Mg2+ or Ca2+, adenosine triphosphate (ATP), and 1 microM free Pb2+ to capture enzymatically released phosphate ions. Electron-dense staining precipitates were found to be associated with the plasmalemma and its tortuous invaginations, and the transverse components of the T-system membrane and its associated proliferated networks. Enzymatic analysis of microsomal fractions isolated from 7-day-old and 90-day-old normal and dystrophic muscle showed a complex behavior. Specific activity of "basic" ATPase decreased with maturity in normal and dystrophic animals. The specific activities of the surface membrane associated enzymes, leucyl beta-naphthylamidase, adenylate cyclase, and guanylate cyclase, remained at various elevated levels in the mature dystrophic animals, in contrast to the normal muscle, which showed decreases in the specific activity of all three enzymes with maturation. The persistent high levels in some but not all enzyme activities in 90-day-old dystrophic muscle indicates a complicated developmental pattern in the dystrophic chicken muscle.
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PMID:Biochemical and cytochemical comparison of surface membranes from normal and dystrophic chickens. 611 29

The effect of sulfhydryl compounds on binding of the beta-adrenergic antagonist (-)-[3H]dihydroalprenolol [(-)-[3H]DHA] to a microsomal fraction from rabbit skeletal muscle was examined. Inhibition of binding by a variety of adrenergic agonists and antagonists and the effects of these agents on adenylate cyclase were consistent with the beta-adrenergic receptor in this tissue being of the beta 2-subtype. Binding of (-)-[3H]DHA was reduced by incubating the membranes with dithiols such as dithiothreitol (DTT), 1,3-dimercapto-2-propanol and 1,4-dimercaptobutane; monothiols were much less potent. DTT-induced decline in (-)-[3H]DHA binding resulted primarily from a decrease in receptor number. Inactivation was partially reversed by the oxidant H2O2. Binding sites could be locked in the inactivated state by incubating DTT-treated membranes with the alkylating agent iodoacetamide. Both beta-adrenergic agonists and antagonists protected against inactivation. Adenylate cyclase activity in the membranes was increased by DTT. The enzyme was rapidly inactivated by H2O2, and this could be partially reversed by DTT. It is concluded that the beta-adrenergic receptor of skeletal muscle contains an essential disulfide moiety which can be inactivated by reducing dithiols. Adenylate cyclase, on the other hand, contains at least one essential sulfhydryl which is preserved by dithiols.
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PMID:Inactivation of the beta-adrenergic receptor in skeletal muscle by dithiols. 613 19


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