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 effect of inhibiting adenosine-metabolizing enzymes on sperm fertilizing ability was studied to investigate a possible role for endogenously generated adenosine in the regulation of capacitation. The compounds used have been shown to be effective inhibitors of the relevant enzymes in similarly incubated mouse sperm suspensions. Inhibition of 5'-nucleotidase activity with alpha, beta-methylene adenosine 5'-diphosphate (AMPCP), to reduce available endogenous adenosine, caused a dose-dependent inhibition of the fertilizing ability of partially capacitated spermatozoa, which was significant with 100 and 250 microM AMPCP. Conversely, inhibition of adenosine deaminase with 100 nM coformycin, to increase available endogenous adenosine, promoted the fertilizing ability of partially capacitated spermatozoa when the fertilization rate of control suspensions was low. However, coformycin had no effect on sperm suspensions with moderate fertilizing ability, and it inhibited fertilizing ability when added to capacitated spermatozoa. These data are consistent with a promotion of the early stages of capacitation by endogenously generated adenosine and suggest that sensitivity to adenosine changes as capacitation proceeds. Because the majority of adenosine-metabolizing enzyme activity residues in or is directed toward the extracellular compartment in such suspensions, these effects of adenosine may be mediated at the outer surface of the cell. By interacting with receptors on adenylate cyclase, externally produced adenosine could modulate intracellular levels of cyclic adenosine monophosphate (cAMP), thereby influencing fertilizing ability.
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PMID:Inhibition of adenosine-metabolizing enzymes modulates mouse sperm fertilizing ability: a changing role for endogenously generated adenosine during capacitation. 285 33

The penetration of Bordetella pertussis adenylate cyclase into various mammalian cells exhibits similar kinetics; the accumulation of both intracellular cyclase activity and cyclic AMP is rapid, reaching constant levels after 15-60 min of incubation. The kinetics of enzyme penetration into turkey erythrocytes is different; cyclase activity and cyclic AMP accumulate linearly and do not reach constant levels even after 6 h of incubation. In the preceding paper [Friedman, Farfel & Hanski (1987) Biochem. J. 243, 145-151] we have suggested that the constant level of intracellular cyclase activity reflects a steady state formed by continuous penetration and intracellular inactivation of the enzyme. In contrast with other mammalian cells, no inactivation of cyclase is observed in turkey erythrocytes. These results further support the notion that there is continuous penetration and deactivation of the invasive enzyme in mammalian cells. A 5-6-fold increase in specific activity of the invasive cyclase is detected in a pellet fraction of human lymphocytes in which a similar increase in specific activity of the plasma-membrane marker 5'-nucleotidase is observed. A similar increase in the invasive-cyclase specific activity is detected in a membrane fraction of human erythrocytes. Cyclase activity in a membrane-enriched fraction of human lymphocytes reached a constant level after 20 min of cell exposure to the enzyme. Similar time courses were observed for accumulation of cyclase activity and cyclic AMP in whole lymphocytes [Friedman, Farfel & Hanski (1987) Biochem, J. 243, 145-151]. We suggest therefore that cyclic AMP generation by the invasive enzyme as well as the intracellular inactivation process occur while it is associated with a membrane fraction identical, or closely associated, with the plasma membrane.
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PMID:The invasive adenylate cyclase of Bordetella pertussis. Intracellular localization and kinetics of penetration into various cells. 288 20

Regulation of coronary blood flow (CBF) is a complex process in which many neural, mechanical, myogenic and metabolic factors are involved and is largely controlled by local factors. Our recent results suggest that CBF and oxygen delivery to cardiac tissue is regulated according to the actual needs of the tissue, determined by oxygen consumption in the mitochondrial respiratory chain, controlled by the energy state of the cell. Several substances have been proposed to serve as messengers between the cardiac myocyte and the vascular smooth muscle cells. Abundant evidence has been accumulated showing that adenosine is an important regulator of CBF, its effects being thought to be mediated by binding to specific external or internal surface receptors, with regulatory link to adenylate cyclase. There is also evidence that adenosine formation takes place intracellularly, predominantly via a cytosolic 5'-nucleotidase. The intracellular level of adenosine is thought to be under delicate control by adenosine producing and metabolizing enzymes. Several arachidonic acid metabolites, especially prostacyclin, are also involved in the regulation of coronary circulation. The physiological significance of atrial natriuretic factor, which also seems to regulate CBF, cannot be established at this stage.
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PMID:Regulation of coronary blood flow. 295 5

Adenylate cyclase and 5'-nucleotidase activities in rat liver plasma membranes were assayed in vitro in the presence of 4-hydroxy-2,3-trans-nonenal (HNE), a major end-product of microsomal lipid peroxidation. Both basal and glucagon-stimulated adenylate cyclase were inhibited in a dose-dependent manner, even at micromolar HNE concentrations, whereas fluoride-stimulated activity increased. A biphasic, dose- and time-dependent effect was noted when the basal activity was monitored at increasing doses. 5'-Nucleotidase activity was also decreased by HNE, but only at millimolar concentrations. These findings are related to the view that aldehydes, especially HNE, may act as diffusible cytotoxic compounds when lipid peroxidative derangement of membrane lipids is provoked by toxic conditions.
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PMID:Effects of 4-hydroxynonenal on adenylate cyclase and 5'-nucleotidase activities in rat liver plasma membranes. 298 58

A tissue disruption technique leading to the separation of thyroid epithelial cell components from interfollicular material has been used to study the distribution and the properties of membrane adenylate cyclase originating from intraglandular thyroid and non-thyroid cells. Bovine thyroid fragments were forced through a metallic sieve. The material which filtrates was composed of open cells and cell debris (fraction A); the material remaining on the sieve contained the basal lamina and the interfollicular material as shown by photon and electron microscopic observations (fraction B). Homogenates (HA and HB) were prepared from fractions A and B and centrifuged on a 41% sucrose layer to prepare membrane fractions: MA and MB, which were tested for the presence of adenylate cyclase, TSH-responsive adenylate cyclase and 125I-labelled TSH binding activity. HA and HB contained respectively 70% and 30% of the total thyroid adenylate cyclase activity. MA and MB were similarly enriched in 5'-nucleotidase and adenylate cyclase: 8- to 10-fold as compared to the corresponding homogenates. MA and MB exhibited a marked difference in the response to TSH: TSH either alone or in the presence of Gpp(NH)p stimulated the adenylate cyclase of MA and did not have any effect on MB. Fractionation of MA by isopycnic centrifugation on Percoll gradients yielded a membrane peak exhibiting a TSH-responsive adenylate cyclase activity and a 125I-labelled TSH binding activity displaceable by an excess of unlabelled TSH. A membrane peak at the same density was obtained from MB but its adenylate cyclase did not respond to TSH and there was no specific binding of labelled TSH. Our data indicate that an important fraction of membrane adenylate cyclase of the thyroid does not seem to be coupled with TSH receptor; the major part of this fraction (MB) likely originates from intraglandular non-thyroid epithelial cells. The separation of this membrane fraction from the thyroid cell plasma membrane fraction (MA) allows to increase the response of this latter fraction to TSH.
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PMID:Separation and analysis of two plasma membrane fractions from bovine thyroid which differ in TSH binding and TSH activation of adenylate cyclase. 299 9

The enzyme activity of Na+-K+-ATPase, Mg++-ATPase, 5'-nucleotidase and adenylate cyclase was cytochemically detected, at the ultrastructural level, in normal mouse peritoneal macrophages Trypanosoma cruzi. Reaction product, indicative of the enzyme activity, was seen in association with the plasma membrane of the macrophage, showing an homogeneous distribution. No reaction product indicative of Na+-K+-ATPase, Mg++-ATPase or adenylate cyclase activity was seen within the cell. Reaction product, indicative of 5'-nucleotidase activity, was seen in cytoplasmic vacuoles. Macrophages incubated in the presence of T. cruzi ingest this parasite which can be seen within membrane-bounded cytoplasmic vacuoles (phagosomes). No activity of the plasma membrane-associated enzymes was seen in the membrane lining vacuoles containing parasites. This observation, together with others previously reported, suggest that the macrophage possesses mechanisms which determine the components of the plasma membrane which are interiorized during the process of endocytosis.
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PMID:The fate of plasma membrane macrophage enzyme markers during endocytosis of Trypanosoma cruzi. 300 76

Neuronal membrane enzyme activities were determined in naive and ethanol-treated (30 min after 2 g/kg) male and female rats of lines developed for more (ANT) and less (AT) ethanol-induced motor impairment. Ethanol did not affect acetylcholinesterase, (Na+K)-ATPase or 5'-nucleotidase activities, but adenylate cyclase activities were lowered in both cerebellum and cerebrum. Cerebral acetylcholinesterase activities were higher in ANT than AT rats. No consistent line difference was observed regarding (Na+K)-ATPase activities. Slightly higher cerebellar 5'-nucleotidase activities were found in the ANT line. Cerebellar adenylate cyclase levels were substantially higher in the AT line. No line differences were displayed in the activation of adenylate cyclase activity by dopamine or norepinephrine. It is concluded that ethanol in vivo may inhibit neuronal adenylate cyclase activity and that cerebellar phosphorylation may be a regulator of motor impairment. Cholinergic mechanisms may also be connected to the ethanol-induced motor impairment.
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PMID:Neuronal membrane enzymes in rat lines selected for differential motor impairment by ethanol. 301 92

Inhibition of cardiac adenylate cyclase by adenosine receptor agonists was reinvestigated in a more homogeneous sarcolemmal vesicular preparation than used in a previous study. Microsomal particles obtained by differential centrifugation were further fractionated on a shallow density gradient of Percoll. Two populations of plasma membrane vesicles were partially resolved. Identical peaks were identified for adenylate cyclase activity and [3H]ouabain binding, whereas 5'-nucleotidase activity and beta-adrenoceptor binding displayed an additional peak at higher density, where angiotensin converting enzyme, a marker for endothelial plasma membranes, was at maximal activity. Significant inhibition by N6-cyclohexyladenosine (CHA), as measured in each fractionation step following homogenization, was observed only at the activity peak of adenylate cyclase. Moreover, analysis of the degree and rank order of potency of several adenosine analogs was indicative for interaction with A1-adenosine receptors. Accordingly, the peak in adenosine receptor binding, using (-)[125I]iodo-N6-hydroxyphenyl-isopropyladenosine as the radioligand, coincided with CHA-inhibitable adenylate cyclase activity. By contrast, adenylate cyclase was slightly stimulated by CHA in the higher density range, an action suggested to be mediated via A2-adenosine receptors, which recently have been demonstrated to exist on guinea-pig coronary endothelium. It is concluded that the full extent of adenosine receptor-mediated adenylate cyclase inhibition in the heart is only to be demonstrated if contamination of the sarcolemmal preparation with endothelial membrane components is kept to a minimum.
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PMID:Cardiac sarcolemmal purity is essential for the verification of adenylate cyclase inhibition via A1-adenosine receptors. 301 95

Effects of hypothyroidism on heart sarcolemmal activities were examined by using membrane preparations obtained by two different methods from rats treated with propylthiouracil for 6 to 8 weeks. ATP-independent Ca2+ binding, sialic acid and phospholipid content, Ca2+ ATPase, Mg2+ ATPase and adenylate-cyclase were not altered in membranes isolated by the hypotonic shock-LiBr treatment method from hypothyroid hearts. On the other hand, depressed activities of ouabain sensitive Na+-K+ ATPase and 5'-nucleotidase were observed in this hypothyroid preparation. Sarcolemma isolated by the sucrose density gradient procedure from hypothyroid hearts exhibited lower ouabain-sensitive Na+-K+ ATPase and higher ATP-dependent Ca2+ binding as well as Ca2+ stimulated ATPase without any changes in the 5'-nucleotidase, adenylate cyclase and Mg2+-ATPase activities. The activation of ATP-dependent Ca2+ binding and Ca2+ stimulated ATPase by calmodulin in the hypothyroid preparation was greater than the control; these effects of calmodulin were blocked by trifluoperazine. The results suggest some specific changes in the heart sarcolemmal Ca2+-pump during the development of hypothyroidism.
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PMID:Sarcolemmal Ca2+-binding and enzyme activities in myocardium from hypothyroid rat. 302 94

Brush borders and plasma membranes have been purified from mucosal epithelial cells of rabbit ileum under control conditions and after treatment for 3 hr with cholera toxin in vivo. The activity of several enzymes in these preparations was measured. It was concluded that adenyl cyclase, like NaK-ATPase, seems not to be a normal constituent of brush borders. Both these enzymes are present in plasma membrane preparations derived largely from the basal and lateral margins of the epithelial cells, both may be phospholipid dependent enzymes and both are affected by cholera toxin. Adenyl cyclase activity is increased while NaK-ATPase is decreased. The activities of alkaline phosphatase, leucineaminopeptidase, 5'-nucleotidase, glucose-6-phosphatase, and Mg-ATPase were not found to be affected by the toxin. Cholera toxin, which makes contact with the luminal side of the epithelial cells, in the natural disease and in the experimental model, would appear to exert its pathologic effect on adenyl cyclase at the opposite (basal and lateral) side of the cells.
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PMID:Localization of the action of cholera toxin on adenyl cyclase in mucosal epithelial cells of rabbit intestine. 434 29


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