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 regulation of three Salmonella typhimurium phosphatases in reponse to different nutritional limitations has been studied. Two enzymes, an acid hexose phosphatase (EC 3.1.3.2) and a cyclic phosphodiesterase (EC 3.1.4.d), appear to be regulated by the cyclic adenosine 3' ,5'-monophosphate (AMP) catabolite repression system. Levels of these enzymes increased in cells grown on poor carbon sources but not in cells grown on poor nitrogen or phosphorus sources. Mutants lacking adenyl cyclase did not produce elevated levels of these enzymes in response to carbon limitation unless cyclic AMP was supplied. Mutants lacking the cyclic AMP receptor protein did not produce elevated levels of these enzymes in response to carbon limitation regardless of the presence of cyclic AMP. Since no specific induction of either enzyme could be demonstrated, these enzymes appear to be controlled solely by the cyclic AMP system. Nonspecific acid phsphatase activity (EC 3.1.3.2) increased in response to carbon, nitrogen, phosphorus, or sulfur limitation. The extent of the increase depended on growth rate, with slower growth rates favoring greater increases, and on the type of limitation. Limitation for either carbon or phosphorus resulted in maximum increases, whereas severe limitation of Mg2+ caused only a slight increase. The increase in nonspecific acid phosphatase during carbon limitation was apparently not mediated by the catabolite repression system since mutants lacking adenyl cyclase or the cyclic AMP receptor protein still produced elevated levels of this enzyme during carbon starvation. Nor did the increase during phosphorus limitation appear to be mediated by the alkaline phosphatase regulatory system. A strain of Salmonella bearing a chromosomal mutation, which caused constitutive production of alkaline phosphatase (introduced by an episome from Escherichia coli), did not have constitutive levels of nonspecific acid phosphatase.
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PMID:Regulation of two phosphatases and a cyclic phosphodiesterase of Salmonella typhimurium. 19 13

Nuclei from purified human peripheral lymphocytes were prepared by incubations with Triton X-100 to disrupt the cells, followed by sucrose-density gradient centrifugation. The nuclei were pure as judged by phase-contrast microscopy and had low contents of non-nuclear marker enzymes. In addition, nuclei prepared from lymphocytes surface-labelled with 125I had only 2-7% of the radioactivity bound to intact lymphocytes. At 3.3 mM-Ca2+ and 100 micronM-ATP a fluoride-sensitive adenylate cyclase was demonstrated in nuclei prepared in 0.2% Triton X-100 or 0.33% Triton X-100. There was linear accumulation of cyclic AMP for 10 min in both preparations. The apparent Km for ATP was 90 micronM. Adenylate cyclase activity was augmented by 1.0 mM-Mn2+ and inhibited at higher concentrations. Ca2+ showed two peaks of stimulation, at 1.0-2.5 mM- and above 10 mM-Ca2+. Mg2+ was inhibitory at all concentrations. EDTA OR EGTA only slightly decreased adenylate cyclase activity, suggesting that another metal ion may be necessary for activity. Adenylate cyclase activity was stimulated by 10mM-isoproterenol and 10 micronM-adrenaline in the presence of a phosphodiesterase inhibitor. Phytohaemagglutinin and prostaglandin E1 alone or in combination with isoproterenol had no effect on nuclear adenylate cyclase activity in either nuclei preparation. These results indicate that human lymphocyte nuclei contain one or several adenylate cyclases which differ from adenylate cyclases found in other subcellular fractions of these cells with regard to their bivalentcation requirements and responsiveness to pharmacological agents.
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PMID:Adenylate cyclase activity in lymphocyte subcellular fractions. Characterization of a nuclear adenylate cyclase. 19 78

The effects of chlofibrate on the adenylate cyclase system of human adipocytes were studied. Clofibrate reduced basal as well as hormone-NaF)stimulated adenylate cyclase activities to about the same extent (45% inhibition at 1 mg/ml clofibrate). The relative extent of hormonal stimulation was not altered by this compound. The inhibitory action of clofibrate was non-competitive with respect to the substrate ATP and cofactors (Mg2+-ions). Inhibition of enzyme activity was detectable after 2.5 min. Our results suggest that the antilipolytic activity of clofibrate is mediated via inhibition of the catalytic subunit of the fat cell adenylate cyclase.
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PMID:Effects of clofibrate on the human fat cell adenylate cyclase system. 19 90

We have solubilized adenylate cyclase in a relatively stable form from rat adrenal membranes. The solubilized enzyme elutes on a column of Sepharose 4BR as a distinct peak with a higher molecular weight than the soluble fractions which bind 125I-ACTH. Both the soluble and membrane bound enzymes are activated by NaF and Gpp(NH)p, and both have similar affinities for MgATP. While the membrane bound enzyme is activated similarly by either Mg2+ or Mn2+, the soluble enzyme is more fully activated by Mn2+. Pretreatment of adrenal membranes with NaF or Gpp(NH)p before the addition of detergent enhances recovery of soluble enzyme activity, while recovery of activity in the unsolubilized membrane pellet is unchanged. In contrast, addition of ACTH prevents solubilization of the enzyme and greatly increases its recovery in the pellet. This observation is consistent with the theory that action of the hormone on a receptor subunit leads to an association between the receptor and a catalytic subunit. Such an association might make it more difficult to remove the enzyme from the surrounding lipid matrix of the membrane.
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PMID:Properties of adenylate cyclase solubilized from rat adrenal membranes: effects of ACTH and other stimulators on solubilization. 20 80

Protein kinase that phosphorylated histone and lesser amounts of protamine was demonstrated in human heart. It was activated three times by 10(-6) M cyclic adenosine 3':5'-monophosphate (cAMP) and by 10(-3) M other cyclic nucleotides. Km values for cAMP, ATP, Mg2+, and Co2+ were about 2 X 10(-8) M, 4 X 10(-5) M, 2 X 10(-3)M, and 1.7 X 10(-4) M, respectively. On DEAE cellulose column, the main peak of the enzyme eluted at high NaCl concentration. On Sephadex G-200 gel filtration the majority of the holoenzyme eluted at a peak corresponding to a molecular weight of about 300,000. There was an additional peak corresponding to a molecular weight of about 400,000, with relatively high cAMP binding compared to kinase activity. Right atrium and ventricle showed significantly higher enzyme activities than left atrium and ventricle and interventricular septum. On multivariate analysis of the enzyme activity versus 12 clinical and pathological findings of 122 cases, cardiac hypertrophy and coronary sclerosis were slight but significant negative contributors to the enzyme activity. Multiple correlation coefficient was low, indicating the enzyme activity remained at a relatively stable level, despite different clinical situations. This may be suitable for control of intracellular events through the membrane adenylate cyclase system.
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PMID:An adenosine 3':5'-monophosphate-dependent protein kinase from human heart. 20 85

Activities of adenylate cyclase in homogenates were reduced, whereas those of phosphodiesterases were elevated in hearts of myopathic hamsters (BIO 82.62). Affinities for either Mg2+ or ATP of cyclase were unaffected in myopathy. Ca2+ stimulation particulate phosphodiesterases was not observed in myopathy. Although the cardiac phosphorylase content was reduced at the advanced stages of myopathy,-AMP/+AMP ratios remained similar to those found in normal hearts.
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PMID:Adenylate cyclase, cyclic nucleotide phosphodiesterase, and phosphorylase activity of cardiomyopathic hamster hearts. 20 98

An assessment was made of some of the basic parameters responsible for the modulation of adenylate cyclase activity in a bovine adrenocortical plasma-membrane preparation. When determined at 0.1 mM-ATP, basal adenylate cyclase activity increased with increasing MgCl2 concentrations, whereas in the presence of corticotropin activity was essentially maximal at 10mM-MgCl2; high concentrations (25mM) of MgCl2 inhibited adenylate cyclase activity determined in the presence of both corticotropin and GTP. At all MgCl2 concentrations, corticotropin and GTP activated the enzyme in a synergistic fashion. The magnitude of the stimulation of basal activity produced by corticotropin was a function of Mg2+ concentration, whereas that produced by GTP appeared largely independent of Mg2+ concentration. Adenylate cyclase activity in the bovine adrenal membrane was half-maximally stimulated by corticotropin concentrations in the range 0.3--1.0 nM. The concentration of corticotropin evoking half-maximum response was not significantly affected by raising the free Mg2+ concentration from 0.4 to 4.9 mM, nor by the presence of GTP. In the presence of GTP, high concentrations (over 1 micrometer) of corticotropin inhibited adenylate cyclase activity, although no inhibition was apparent in the absence of guanine nucleotide.
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PMID:Modulation of the response of bovine adrenocortical adenylate cyclase to corticotropin. 20 64

Purified bovine pituitary plasma membranes possess two specific LH-RH binding sites. The high affinity site (2.5 X 10(9) l/mol) has low capacity (9 X 10(-15) mol/mg membrane protein) while the low affinity site 6.1 X 10(5) l/mol) has a much higher capacity (1.1 X 10(-10) mol/mg). Specific LH-RH binding to plasma membranes is increased 8.5-fold during purification from homogenate whilst adenylate cyclase activity is enriched 7--8-fold. Distribution of specific LH-RH binding to sucrose density gradient interface fractions parallels that of adenylate cyclase activity. Mg2+ and Ca2+ inhibit specific [125I]LH-RH binding at micromolar concentrations. Synthetic LH-RH, up to 250 microgram/ml, failed to stimulate adenylase cyclase activity of the purified bovine membranes. Using a crude 10,800 g rat pituitary membrane preparation, LH-RH similarly failed to activate adenylate cyclase even in the presence of guanyl nucleotides. These data confirm the presence of LH-RH receptor sites on pituitary plasma membranes and suggest that LH-RH-induced gonadotrophin release may be mediated by mechanisms other than activation of adenylate cyclase.
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PMID:LH-RH binding to purified pituitary plasma membranes: absence of adenylate cyclase activation. 21 61

Adenylate cyclase can be resolved into at least two proteins, a thermolabile, N-ethylmaleimide-sensitive component and a second protein (or proteins) that is more stable to either of these treatments. Neither component by itself catalyzes the formation of cyclic AMP using MgATP as substrate. However, mixture of the two reconstitutes MgATP-dependent fluoride- and guanyl-5'-yl imidodiphosphate (Gpp(NH)p)-stimulatable adenylate cyclase activity. The more stable component can be resolved from the first in various tissues or cultured cells by treatment of membrnes or detergent extracts with heat or N-ethylmaleimide. The two proteins have also been resolved genetically in two clonal cell lines that are deficient in adenylate cyclase activity. An adenylate cyclase-deficient variant of the S49 lymphoma cell (AC-) contains only the thermolabile activity, while the activity of the more stable protein is found in a complementary hepatoma cell line (HC-1). In addition, AC-S49 cell plasma membranes contain MnATP-dependent adenylate cyclase activity. The protein that catalyzes this reaction appears to be the same as that which can combine with the thermostable component to reconstitute Mg2+-dependent enzyme activity because both activities co-fractionate by gel exclusion chromatography and sucrose density gradient centrifugation, both activities have identical denaturation kinetics at 30 degrees C, and both activities are stabilized at 30 degrees C and labilized at 0 degree C by various nucleotides and divalent cations with similar specificity. It is thus hypothesized that the thermolabile factor is the catalytic subunit of the physiological adenylate cyclase and that the Mn2+-dependent activity is a nonphysiological expression of the catalytic protein. The thermostable moiety of the enzyme, which is proposed to serve a regulatory function, appears to consist of two functional components, based upon differential thermal lability of its ability to reconstitute hormone-, NaF-, or Gpp(NH)p-stimulated adenylate cyclase activity. These components have not, however, been physically separated. The thermolabile and thermostable components can interact in detergent solution or in a suitable membrane. Mixing of the detergent-solubilized regulatory component with AC-membranes that contain only the catalytic protein and beta-adrenergic receptors reconstitutes catecholamine-stimulatable adenylate cyclase activity; however, addition of the catalytic protein to membranes that contain receptor and the regulatory component yields MgATP-dependent enzymatic activity that is unresponsive to hormone.
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PMID:Reconstitution of hormone-sensitive adenylate cyclase activity with resolved components of the enzyme. 21 Jan 83

The properties of a number of enzyme activities of the superovulated rat ovary have been studied to establish optimal assay conditions and specific assay procedures for each activity. The activities were chosen on the basis of their extensive use in other tissues of the rat as marker enzymes for the major cell organelles. Homogenates of superovulated rat ovaries were subjected to fractionation by differential rate centrifugation, and sedimentation profiles were constructed for each marker enzyme activity. The various subcellular fractions were also monitored by electron microscopy. The enrichment of fractions with particular organelles by electron microscopy, and enrichment of the appropriate organelle marker enzyme activities correlated well. Sedimentation profiles of a number of plasma membrane marker enzymes demonstrated a marked discrepancy between hCG-binding activity, and 5'-nucleotidase-, alkaline phosphatase-, and Mg2+-dependent ATP-ase on the one hand, and basal, hCG-stimulated, and fluoride-stimulated adenylate cyclase activities on the other hand. Fractions enriched in hCG-binding and adenylate cyclase activities were subjected to further fractionation on discontinuous sucrose density gradients. The distributions of the various plasma membrane markers again indicated a partial dissociations between hCG-binding and adenylate cyclase activities of luteinized rat ovaries, suggesting the existence of two distinct major plasma membrane populations, with different buoyant densities, marker enzyme profiles and adenylate cyclase and hormone-binding levels.
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PMID:Interactions of gonadotropins with corpus luteum membranes. I. Properties and distributions of some marker enzyme activities after subcellular fractionation of the superovulated rat ovary. 21 56


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