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:3.1.4.1 (phosphodiesterase)
18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Venoms from 20 species of stinging Hymenoptera, including nine species of ants and nine species of social wasps, were quantitatively analyzed for the following enzymic activities: phospholipase A, hyaluronidase, lipase, esterase, protease, acid phosphatase, alkaline phosphatase and phosphodiesterase. Phospholipase and hyaluronidase were present in all the venoms, with activity levels generally higher among the wasps than the ants (P less than 0.05). Lipase was present in high activity in several social wasp venoms and one ant venom, in low levels in two other ant venoms and absent from four tested snake venoms. Two-carbon esterase activity was present in the venoms of five social wasps and one ant. Non-specific protease was present at very high activity levels in the venoms of an army ant species and was also present in the venoms of a social wasp and another ant. Acid phosphatase activity was present in eight of the nine ant venoms, but was essentially absent from all the social wasp venoms. Alkaline phosphatase activity was clearly detectable in the venoms of only two species of ants. Phosphodiesterase, an enzyme not previously detected in insect venoms, was present in the venoms of three closely related ant species. Venoms with generally high enzymic activities included those of Polistes infuscatus, Vespula (V.) squamosa and Pogonomyrmex badius; those with low activities included Dolichovespula maculata, Apoica pallens and Dasymutilla lepeletierii. The 20 venoms were ranked according to overall activity levels using the eight enzyme activities plus lethal, hemolytic and pain-inducing activities. They were also compared phylogenetically using these 11 activities.
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PMID:Comparative enzymology of venoms from stinging Hymenoptera. 354 39

1. The rise in clearing-factor lipase activity that occurs when epididymal fat bodies from starved rats are incubated in appropriate media in vitro is inhibited in the presence of 6-N-2'-O-dibutyryl-3',5'-(cyclic)-AMP (1mm). 2. Inhibition occurs at a concentration of glucose in the incubation medium of 1.3mg./ml. or less, but not at a glucose concentration of 2.4mg./ml., unless caffeine (1mm), an inhibitor of 3',5'-(cyclic)-nucleotide phosphodiesterase, is also present. Caffeine (5mm) alone inhibits the rise in clearing-factor lipase activity at a glucose concentration of 2.4mg./ml. of medium. 3. The concentration of free fatty acids in the epididymal fat bodies normally falls during incubations in vitro as the rise in clearing-factor lipase activity occurs. In the presence of 1mm-6-N-2'-O-dibutyryl-3',5'-(cyclic)-AMP, however, either the tissue free fatty acid concentration is increased or it does not fall to the same extent. The concentration of glucose in the incubation medium is important in determining the direction and extent of the changes in tissue free fatty acid concentration that occur in the presence of 6-N-2'-O-dibutyryl-3',5'-(cyclic)-AMP. 4. Free fatty acid concentrations in epididymal fat bodies in vivo rise as the clearing-factor lipase activity of the tissue falls during starvation. 5. The possibility that the concentration of 3',5'-(cyclic)-AMP in adipose tissue may regulate clearing-factor lipase activity, and that the regulation may occur through effects of the nucleotide on tissue free fatty acid concentrations, is discussed.
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PMID:Clearing-factor lipase in adipose tissue. A possible role of adenosine 3',5'-(cyclic)-monophosphate in the regulation of its activity. 430 48

The effects of different adrenergic agents on high density lipoprotein (HDL) cholesterol concentration and on the neutral NaCl-resistant triacylglycerol hydrolase (liver lipase) activity of the liver were studied in rats. Treatment of rats with the beta-blockers metoprolol, atenolol or propranolol led to a lowering of the HDL-cholesterol (esterified and non-esterified) content. The alpha 1-antagonist prazosin had no effect. Administration of norepinephrine for 10 days resulted in an increase of HDL non-esterified cholesterol. This effect of norepinephrine was largely abolished by prazosin, but not by propranolol. In normal rats the liver lipase activity was not influenced by alpha- or beta-blockade. Adrenergic stimulation, either short-term (by diethyl ether stress) or long-term (by norepinephrine treatment), led to a lowered liver lipase activity. The lipase activity was restored by prazosin but not by propranolol. The apparent involvement of the alpha 1-receptor in the regulation of liver lipase activity was further studied in vitro. Blockade of alpha- or beta-receptors with prazosin or propranolol did not affect the secretion of the liver lipase activity by isolated parenchymal liver cells. Stimulation of alpha- or beta-receptors by epinephrine led to a lower secreted lipase activity. Selective stimulation by isoprenaline had no effect. The effect of epinephrine could be abolished by prazosin but not by propranolol. Vasopressin and the calcium ionophore A23187 also lowered the secretion of liver lipase activity in vitro. Glucagon and/or the phosphodiesterase inhibitor Ro 20-1724 had no effect. These results indicate an involvement of the alpha 1-receptor in the regulation of liver lipase activity at the level of synthesis or secretion of the lipase. The effect of the alpha 1-receptor is presumably mediated through changes in the intracellular free calcium concentration. The effect of adrenergic modulation on HDL-cholesterol concentrations can partly be explained through modification of the liver lipase activity.
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PMID:Regulation of liver lipase. II. Involvement of the alpha 1-receptor. 614 7

Triacylglycerol breakdown (lipolysis) results from a series of reactions culminated by activation of "hormone-stimulated" triacylglycerol lipase, an enzyme unique to adipose tissue. We have studied various components of the lipolytic process in human omental adipocyte precursors differentiating in culture. The levels of cyclic AMP, the "second messenger" of lipolytic hormones, were about sixfold higher in fat cell precursors than those in abdominal skin fibroblasts. L-Isoproterenol resulted in significant elevation of cyclic AMP levels in both cell types. Preincubation of intact adipocyte precursors with insulin resulted in significant enhancement of "low Km" cyclic AMP phosphodiesterase activity; in contrast, this hormone had no effect on fibroblast phosphodiesterase activity, a distinctive biochemical difference despite the morphological similarities between the two cell types during the early stages of adipocyte precursor maturation. Incubation of adipocyte precursors with isoproterenol resulted in the release of fatty acids into the medium, findings indicative of "hormone-stimulated" lipase activity and, hence, the operation of the entire "lipolytic cascade"; isoproterenol-stimulated lipolysis was inhibited by insulin. Release of fatty acids from fibroblasts was not observed. Thus, "hormone-stimulated" lipolysis and insulin stimulation of cyclic AMP phosphodiesterase activity are expressed during early stages of human adipocyte precursor differentiation.
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PMID:Cyclic AMP metabolism and lipolysis in cultured human adipocyte precursors. 624 74

The purpose of the present study was to determine the possible interaction of cyclic AMP (cAMP) and the synthesis of prostacyclin [measured as immunoreactive 6-keto-prostaglandin (PG)F1 alpha] elicited by the beta adrenergic receptor agonist isoproterenol (ISOP), in freshly dissociated rabbit ventricular myocytes. ISOP (10(-13) to 10(-11) M) increased 6-keto-PGF1 alpha synthesis without altering the level of cAMP. Increasing the concentration of ISOP from 10(-10) to 10(-7) M enhanced accumulation of cAMP, which was associated with a decline in 6-keto-PGF1 alpha synthesis. Forskolin (10(-6) M), an activator of adenylyl cyclase, and 3-isobutyl-1-methylxanthine (10(-5) M), an inhibitor of cAMP phosphodiesterase, increased cAMP accumulation and inhibited ISOP-induced 6-keto-PGF1 alpha synthesis. 8-(4-chlorophenylthio) (cpt)-cAMP (10(-7) M) also inhibited ISOP-induced 6-keto-PGF1 alpha production. On the other hand, miconazole (10(-4) M), an inhibitor of adenylyl cyclase, reduced cAMP accumulation and enhanced ISOP-induced 6-keto-PGF1 alpha synthesis in myocytes. Miconazole also attenuated ISOP-, forskolin- and cpt-cAMP-induced increases in protein kinase A activity. The protein kinase A inhibitor H-89 {N-[2-(p-bromocinnamylamino)ethyl] -5-isoquinolinesulfonamide} attenuated the ISOP (10(-7) M)-induced increase in the activity of this enzyme and minimized the decline in 6-keto-PGF1 alpha synthesis produced by 10(-7) M ISOP and the inhibitory effect of cpt-cAMP and forskolin on 6-keto-PGF1 alpha production. 3-Isobutyl-1-methylxanthine, forskolin and cpt-cAMP did not alter the conversion of exogenous arachidonic acid to 6-keto-PGF1 alpha. These data indicate that beta adrenergic receptor activation promotes prostacyclin synthesis in rabbit ventricular myocytes and that cAMP acts as an inhibitory modulator. This action is mediated via activation of protein kinase A, probably by decreasing the activity of the lipase, involved in beta adrenergic receptor-induced arachidonic acid release.
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PMID:Modulation by cyclic AMP of beta adrenergic receptor-stimulated prostacyclin synthesis in rabbit ventricular myocytes. 876 95

Papaverine, despite being a potent phosphodiesterase inhibitor, actually blocks adipocyte lipolysis. The present study was designed to clarify the mechanism of the inhibitory effect of papaverine on lipolysis. Lipolysis, stimulated by either 10 microM isoproterenol or 5 mM dibutyryl cAMP, was significantly inhibited by papaverine (100 microM and above). Papaverine, however, did not affect the isoproterenol-induced increase in the protein kinase A (A-kinase) activity ratio. In cell-free extract from non-stimulated adipocytes, cAMP-stimulated A-kinase activities were almost completely blocked by H-89, a potent inhibitor of A-kinase, but not by papaverine. Thus, the inhibitory effect of papaverine on lipolysis could be responsible for a deficit in step(s) distal to A-kinase activity. Hormone-sensitive lipase activities in the infranatant fraction of centrifuged homogenates of cells, which were maximally stimulated with isoproterenol were significantly reduced. This result indicates that hormone-sensitive lipase redistributes from cytosol to its substrate in lipolytically stimulated cells. Papaverine completely blocked the isoproterenol-induced decrease in lipase activity in the infranatant fraction. These results suggest that papaverine blocks lipolysis through its inhibitory effect on the redistribution of hormone-sensitive lipase.
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PMID:Inhibition of adipocyte lipolysis by papaverine: papaverine can inhibit the redistribution of hormone-sensitive lipase. 1089 95

Genistein is a phytoestrogen found in several plants eaten by humans and food-producing animals and exerting a wide spectrum of biological activity. In this experiment, the impact of genistein on lipogenesis and lipolysis was studied in isolated rat adipocytes. Incubation of the cells (10(6) cells/ml in plastic tubes at 37 degrees C with Krebs-Ringer buffer, 90 min) with genistein (0.01, 0.3, 0.6 and 1 mM) clearly restricted (1 nM) [U-14C]glucose conversion to total lipids in the absence and presence of insulin. When [14C]acetate was used as the substrate for lipogenesis, genistein (0.01, 0.1 and 1 mM) exerted a similar effect. Thus, the anti-lipogenetic action of genistein may be an effect not only of alteration in glucose transport and metabolism, but this phytoestrogen can also restrict the fatty acids synthesis and/or their esterification. Incubation of adipocytes with estradiol at the same concentrations also resulted in restriction of lipogenesis, but the effect was less marked. Genistein (0.1 and 1 mM) augmented basal lipolysis in adipocytes. This process was strongly restricted by insulin (1 microM) and H-89 (an inhibitor of protein kinase A; 50 microM) and seems to be primarily due to the inhibitory action of the phytoestrogen on cAMP phosphodiesterase in adipocytes. Genistein at the smallest concentration (0.01 mM) augmented epinephrine-stimulated (1 microM) lipolysis but failed to potentiate lipolysis induced by forskolin (1 microM) or dibutyryl-cAMP (1 mM). These results suggest genistein action on the lipolytic pathways before activation of adenylate cyclase. The restriction of lipolysis stimulated by several lipolytic agents--epinephrine, forskolin and dibutyryl-cAMP were observed when adipocytes were incubated with genistein at highest concentrations (0.1 and 1 mM). These results prove the inhibitory action of this phytoestrogen on the final steps of the lipolytic cascade, i.e. on protein kinase A or hormone sensitive lipase. Estradiol, added to the incubation medium, did not affect lipolysis. It can be concluded that genistein significantly affects lipogenesis and lipolysis in isolated rat adipocytes.
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PMID:Genistein affects lipogenesis and lipolysis in isolated rat adipocytes. 1128 81

The availability of the complete genome sequence of Bacillus subtilis has allowed the prediction of all exported proteins of this Gram-positive eubacterium. Recently, approximately 180 secretory and 114 lipoprotein signal peptides were predicted to direct protein export from the cytoplasm. Whereas most exported proteins appear to use the Sec pathway, 69 of these proteins could potentially use the Tat pathway, as their signal peptides contain RR- or KR-motifs. In the present studies, proteomic techniques were applied to verify how many extracellular B. subtilis proteins follow the Tat pathway. Strikingly, the extracellular accumulation of 13 proteins with potential RR/KR-signal peptides was Tat-independent, showing that their RR/KR-motifs are not recognized by the Tat machinery. In fact, only the phosphodiesterase PhoD was shown to be secreted in a strictly Tat-dependent manner. Sodium azide-inhibition of SecA strongly affected the extracellular appearance of de novo synthesized proteins, including the lipase LipA and two other proteins with predicted RR/KR-signal peptides. The SecA-dependent export of pre-LipA is particularly remarkable, because its RR-signal peptide conforms well to stringent criteria for the prediction of Tat-dependent export in Escherichia coli. Taken together, our observations show that the Tat pathway makes a highly selective contribution to the extracellular proteome of B. subtilis.
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PMID:Selective contribution of the twin-arginine translocation pathway to protein secretion in Bacillus subtilis. 1221 47

Glucose-induced insulin secretion from isolated, perifused rat islets is pulsatile with a period of about 5-10 min, similar to the insulin oscillations that are seen in healthy humans but which are impaired in Type II diabetes. We evaluated the pattern of enhancement by the potent incretin, glucagon-like peptide 1 (GLP-1). GLP-1 increased the amplitude of pulses and the magnitude of insulin secretion from the perifused islets, without affecting the average time interval between pulses. Forskolin and the phosphodiesterase inhibitor isobutylmethylxanthine had the same effect, suggesting that the effect was due to elevated cAMP levels. The possibility that cAMP might enhance the amplitude of pulses by reducing phosphofructo-2-kinase (PFK-2) activity was eliminated when the liver isoform of PFK-2 was shown to be absent from beta-cells. The possibility that cAMP enhanced pulsatile secretion, at least in part, by stimulating lipolysis was supported by the observations that added oleate had a similar effect on secretion, and that the incretin effect of GLP-1 was inhibited by the lipase inhibitor orlistat. These data show that the physiological incretin GLP-1 preserves and enhances normal pulsatile insulin secretion, which may be essential in proposed therapeutic uses of GLP-1 or its analogues.
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PMID:Glucagon-like peptide 1 and fatty acids amplify pulsatile insulin secretion from perifused rat islets. 1235 35

The goal of the present study was to examine cellular mechanisms that regulate adipose cell metabolism in ovariectomized (OVX) and intact rats that were subjected to long-term (27 weeks) treatment with dehydroepiandrosterone (DHEA). Forty-eight 16-month-old female rats were divided into 4 groups of 9 to 11 animals (intact, intact-DHEA, OVX, OVX-DHEA). Adipose tissue lipoprotein lipase (LPL), hormone-sensitive lipase (HSL), and cyclic adenosine monophosphate (cAMP)-dependent phosphodiesterase (cAMP-PDE) activities were determined, and alpha2-, beta1/beta2-, and beta3-adrenoceptors (ARs) were quantified. DHEA did not affect body weight, fat, or muscle mass in intact rats. The similar retroperitoneal fat pad weight of intact-DHEA rats compared to intact animals was in agreement with the lack of difference in the enzyme activities and AR densities. The increased body weight of OVX rat was paralleled by a greater retroperitoneal adipose tissue mass (P <.01), which was in turn associated with a marked rise in LPL activity (P <.005) and a slight decrease in HSL activity (P <.05) compared to intact animals. OVX-DHEA rats, compared to untreated OVX animals, had a smaller retroperitoneal fat depot, which correlated with a decrease in LPL activity (P <.005) and moderate increase in both HSL activity and beta3-AR density (P <.05). DHEA-treatment lowered fasting insulin and triglyceride levels in both intact and OVX rats (P <.05). Plasma testosterone, androsterone, androstenedione, and androstenediol levels were also significantly increased in both intact-DHEA and OVX-DHEA rats compared to untreated animals (P <.0001). These findings suggest that the antiobesity action of DHEA may be related in part to changes in lipase activities and in beta3-AR density, and that it is dependent on the ovarian status of the animal.
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PMID:Chronic effects of dehydroepiandrosterone on rat adipose tissue metabolism. 1264 61


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