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)

1. Iontophoretic injection of adenosine 3',5'-cyclic monophosphate (cAMP) into identified neurons elicited a slow transient Na+ current whose amplitude and duration were sensitive to altered intracellular pH (pHi), calmodulin blocking drugs, depolarization, and manipulations of internal and external Ca2+. 2. Intracellular acidification between resting pHi to several tenths of a pH unit increased the amplitude of the cAMP-stimulated current and prolonged its duration. 3. Intracellular alkalinization of similar magnitude also increased the amplitude and duration of the current response. The effects of alkalinization were somewhat labile. In cells alkalinized by NH4+-containing salines, washout of NH4+ with normal saline caused acidification and further enhanced the cAMP current response. The immediacy of the increase and the dual acid/basic sensitivity of the response suggest an accommodative process whereby the responsiveness of the cell to cAMP adapts to a maintained pHi. 4. The calmodulin blockers trifluoperazine and N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide increased the amplitude and duration of the current response. Phorbol ester activators of Ca2+/phospholipid-dependent kinase had no effect on the current. 5. Periods of depolarization preceding tests significantly reduced current response amplitude. This effect was dependent on saline Ca2+ and was blocked by Co2+. 6. Intracellular injection of the Ca2+ chelator ethylene glycol-bis(beta-aminoethyl ether)N,N,N',N',-tetraacetic acid also augmented the amplitude and duration of the current response. 7. The above effects are consistent with a possible common site of action on cAMP degradation. This interpretation is consistent with previous evidence for pH-sensitive and Ca2+/calmodulin-dependent cAMP phosphodiesterase activity in Pleurobranchaea nervous tissue.
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PMID:Regulation of cAMP-stimulated ion current by intracellular pH, Ca2+, and calmodulin blockers. 244 21

The aim of this investigation was to substantiate the hypothesis that the vasorelaxant effects of 5-methyl-6-(4-pyridyl)-2H-1,4-thiazin-3(4H)-one (ZSY-27) are mediated by accumulation of intracellular cyclic nucleotides as a consequence of inhibition of cyclic nucleotide phosphodiesterase activity. Both activities of adenosine 3',5'-monophosphate-phosphodiesterase (cAMP-PDE) in the presence of ethylene glycol-bis(beta-aminoethyl ether) N,N,N',N'-tetraacetic acid (EGTA) and guanosine 3',5'-monophosphate-phosphodiesterase (cGMP-PDE) in the presence of calcium-calmodulin from rabbit thoracic aorta were inhibited in a concentration-dependent manner by ZSY-27 (10(-5) - 10(-3) M). The IC50 values for ZSY-27 on cAMP- and cGMP-PDE activity were 2.1 x 10(-4) and 8.8 x 10(-4) M, respectively. Furthermore, ZSY-27 antagonized competitively cAMP-PDE (Ki = 1.9 x 10(-4) M). On the other hand, ZSY-27 exhibited a mixed-type inhibitory pattern, with reduction of both maximum velocity and affinity for the substrate of the cGMP-PDE, with a Ki value of 1.0 x 10(-3) M. Spontaneous myogenic tone of rabbit thoracic aorta was significantly attenuated from 1 min after addition of ZSY-27 (3 x 10(-4) M). Contents of cAMP and cGMP were significantly increased from 1 and 3 min after addition of ZSY-27, respectively. Temporally, relaxant effects of ZSY-27 were associated with increases of cAMP content, but not with that of cGMP content.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Relationship between cyclic nucleotide levels and 5-methyl-6-(4-pyridyl)-2H-1,4-thiazin-3(4H)-one (ZSY-27), a new positive inotropic agent with a vasodilatory action, -induced relaxation of rabbit thoracic aorta. 256 Nov 55

CD-349 (2-nitratopropyl 3-nitratopropyl 2,6-dimethyl-4-(3-nitrophenyl)-1,4-dihydropyridine-3,5-dicarboxylate) inhibited the activity of cyclic AMP phosphodiesterase (PDE) from the porcine coronary artery more effectively than that from the myocardium. Other dihydropyridines, nicardipine and nifedipine, were not tissue selective in inhibiting the cyclic AMP PDE from both sources. CD-349 inhibited cyclic AMP PDE noncompetitively with apparent inhibition constant (K1) values of 6.6 and 4.6 microM for high and low affinity constant (Km) enzymes, respectively. Basal activity of coronary arterial cyclic AMP PDE was decreased to approximately 65% of the control value by 0.2 mM ethylene glycol bis (beta-amino-ethyl ether) N,N,N',N'-tetraacetic acid (EGTA). In the coronary artery, the inhibition of cyclic AMP PDE by CD-349 was weakened in the presence of EGTA, while the inhibition of nicardipine and nifedipine were not affected. EGTA had no influence on the CD-349 induced inhibition of myocardial cyclic AMP PDE. Calmodulin antagonists such as trifluoperazine (TFP) gave substantially the same results as those with CD-349. These results indicate the relative selectivity of the coronary arterial cyclic AMP PDE inhibition by CD-349 and suggest that this selective inhibition is due to blockade of calcium/calmodulin-activated cyclic AMP PDE.
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PMID:Inhibition of adenosine 3',5'-cyclic monophosphate phosphodiesterase by CD-349, a novel 1,4-dihydropyridine derivative: effect of EGTA on the inhibitory activity. 283 Apr 23

Calmodulin tryptic fragments 78-148, 107-148, and 1-77 coupled to Sepharose 4B were used to test the ability of different calmodulin-regulated enzymes to recognize different domains of calmodulin. Fragment 107-148, which contains a single Ca2+-binding domain, does not interact with any of the calmodulin binding proteins. Fragments 1-77 and 78-148, each of which contains two Ca2+-binding domains, have preserved their ability to interact with several calmodulin-dependent enzymes. Most of the calmodulin-regulated enzymes in brain extracts, such as cAMP phosphodiesterase, cAMP-dependent protein kinase, and the calmodulin-stimulated protein phosphatase (calcineurin) interact with fragment 78-148 in a Ca2+-dependent fashion. An ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid-sensitive, calmodulin-independent, p-nitrophenyl phosphatase does not bind to the affinity column and is resolved from calcineurin at this step. Although calmodulin-stimulated protein kinase(s) can interact with fragment 78-148, their interaction is prevented by increased ionic strength even in the presence of Ca2+. Fragment 1-77 exhibits a higher degree of selectivity than fragment 78-148. Only cAMP-dependent protein kinase and cAMP phosphodiesterase bind to fragment 1-77. These results confirm the multiple modes of interaction of calmodulin with its target proteins and provide the basis for a selective purification of calmodulin-regulated enzymes by affinity chromatography on specific calmodulin fragments coupled to Sepharose.
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PMID:Selective affinity chromatography with calmodulin fragments coupled to sepharose. 298 37

Changes in the concentration of cytosolic Ca2+ are assumed to alter the activity of Ca2+-calmodulin-sensitive cyclic nucleotide phosphodiesterase in intact cells. However, this assumption is based on indirect evidence and by analogy from studies of enzyme activities in broken cell systems. We have developed a procedure for estimating the fraction of Ca2+-calmodulin-sensitive phosphodiesterase that is in an activated, ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) sensitive state in intact porcine coronary artery strips. The experimental approach involves homogenization of the strips and assay of cyclic guanosine monophosphate (cyclic GMP) phosphodiesterase activity under conditions that retard changes in the amount of the complex Ca2+-calmodulin-phosphodiesterase. Our findings indicate that cyclic GMP phosphodiesterase in intact coronary artery strips does associate with Ca2+-calmodulin and that interventions that change the concentration of Ca2+ in the cytosol of the intact strip change the extent of this functional association. Exposure to histamine (10 or 100 microM) or 50 mM KCl caused contraction and an increase in EGTA-sensitive cyclic GMP phosphodiesterase activity. Isoproterenol-induced relaxation of tissues that had been caused to contract with 10 microM histamine was accompanied by a reduction in EGTA-sensitive cyclic GMP phosphodiesterase activity to the same level as that present before contraction was initiated.
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PMID:Differences in the association of calmodulin with cyclic nucleotide phosphodiesterase in relaxed and contracted arterial strips. 298 4

Purified calmodulin-stimulated cyclic nucleotide phosphodiesterase from brain, a homodimer of 59-kDa subunits, was activated by limited proteolysis with trypsin, alpha-chymotrypsin, Pronase, or papain and could not be further stimulated by addition of Ca2+ and calmodulin. Proteolysis increased Vmax and had little effect on the Km for cGMP. Treatment with alpha-chymotrypsin in the presence of ethylene glycol bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid (EGTA) produced, sequentially, 57- and 45-kDa peptides from the bovine and 55-, 53-, and 38-kDa peptides from the ovine enzyme. This protease-treated phosphodiesterase exhibited a Stokes radius of 3.9 nm and an S20,w value of 4.55; comparison with the hydrodynamic properties observed for native enzyme (4.3 nm, 5.95 S) strongly suggests a dimeric protein of Mr approximately 80,000-90,000. The proteolyzed species does not interact significantly with calmodulin immobilized on agarose, nor does it show complex formation with 2-dimethylaminonaphthalene-1-sulfonyl-calmodulin even at micromolar concentrations of protein. Proteolysis, in the presence of calmodulin plus Ca2+, fully activated phosphodiesterase, producing the same intermediate peptides; however, final peptides from the bovine and ovine enzymes were 47 and 42 kDa, respectively, indicating a new, specific conformation of the enzyme. When EGTA was added to such incubations, these peptides were cleaved to those of the size seen when proteolysis was carried out entirely in the presence of EGTA. The initial rate of activation was increased by the presence of Ca2+ and calmodulin, suggesting that, in complex, phosphodiesterase exhibits a site with increased susceptibility to proteolysis. Since calmodulin can still interact with a fully activated form of the enzyme, it appears that retention of calmodulin binding can occur concomitantly with damage to that portion of the phosphodiesterase molecule responsible for suppression of its basal catalytic activity.
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PMID:Proteolytic activation of calmodulin-dependent cyclic nucleotide phosphodiesterase. 299 Dec 33

Murine adrenal cortex tumor Y-1 cells contained both soluble and particulate forms of cyclic nucleotide phosphodiesterase (3',5'-cyclic AMP 5'-nucleotide hydrolase, EC 3.1.4.17). The soluble forms of the enzyme comprised 80% of total cellular phosphodiesterase activity. The soluble enzyme(s) hydrolyzed both cyclic AMP and cyclic GMP, with apparent Km values of 125 and 30 microM, respectively. Soluble cyclic AMP phosphodiesterase showed marked inhibition by the calcium chelator, ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid (EGTA), and the anticalmodulin drugs, chlorpromazine, N-(6-aminohexyl)-5-chloro-1-naphthalenesulfonamide (W-7), and calmidazolium. No alteration in soluble cyclic GMP phosphodiesterase activity was observed when cyclic AMP was added to the assay. Resolution of the soluble enzymatic activity by DEAE-cellulose chromatography in the presence of calcium showed two peaks of phosphodiesterase activity. Further purification of one of these peaks on DEAE-cellulose in the presence of EGTA yielded a phosphodiesterase activity peak that was stimulated fivefold by calmodulin. The particulate form of the enzyme hydrolyzed both cyclic AMP anc cyclic GMP; the apparent Km values for these substrates were similar (90 and 100 microM, respectively). Hydrolysis of cyclic GMP by the particulate enzyme was inhibited by cyclic AMP in a concentration-dependent manner with an apparent half-maximal inhibitory concentration of 100 microM. The particulate form of phosphodiesterase was not inhibited by EGTA or anticalmodulin drugs.
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PMID:Multiple forms of cyclic nucleotide phosphodiesterase in a murine adrenal cortex cell line (Y-1). 299 65

Neuropeptide Y (NPY), which co-exists with noradrenaline (NA) in postganglionic sympathetic nerves, was able to potentiate NA-evoked constriction in certain isolated rabbit blood vessels. The phenomenon was observed in the femoral, the gastroepiploic and the pulmonary arteries but not in the femoral or the gastroepiploic veins or in the aorta. Thus, NPY potentiated NA-evoked vasoconstriction predominantly in muscular arteries with alpha-1 adrenoceptors. NPY-related peptides, such as peptide YY and to some extent pancreatic polypeptide shared this ability, whereas calcitonin gene-related peptide or LPLRFamide did not. The mode of action by which NPY potentiates NA-evoked vasoconstriction was analyzed using the femoral artery. Pretreatment of the vessel with cocaine, a blocker of amine re-uptake, or rolipram, an inhibitor of phosphodiesterase, left the potentiation unaffected, whereas Na+ deficiency or ouabain, an inhibitor of Na+/K+-adenosine triphosphatase, abolished this effect of NPY. Nifedipine, a blocker of Ca++ entry, or removal of extracellular Ca++ shortly before the application of NPY had little effect. After prolonged exposure to a Ca++-free medium (with ethylene glycol bis(beta-aminoethyl ether)-N,N'-tetraacetic acid) the maximum response to NA was greatly reduced and the potentiating effect of NPY was abolished. Thus, the potentiation of NA-evoked vasoconstriction by NPY seems to depend upon the presence of Na+ but not upon a Ca++ influx. An intracellular sequestered Ca++ pool appears to play a critical role.
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PMID:Neuropeptide Y potentiates noradrenaline-evoked vasoconstriction: mode of action. 392 74

A sensitive in vitro bioassay for measuring serum follicle-stimulating hormone (FSH) levels has been developed based on the stimulation of estrogen production by cultured rat granulosa cells. In the presence of androstenedione, FSH stimulated estrogen production in a dose-dependent manner. Cell sensitivity to FSH was further enhanced by the addition of diethylstilbestrol, a phosphodiesterase inhibitor, insulin, and human chorionic gonadotropin. Although the inclusion of 4% gonadotropin-free serum from hypophysectomized rats inhibited granulosa cell responsiveness, pretreatment of serum with polyethylene glycol (12%) substantially eliminated the serum interfering effect without loss of FSH activity. In normal male and female rats, serum bioactive FSH levels were low, while castration increased these levels 2.6-and 5.7-fold, respectively. These increases were suppressed by treatment with testosterone propionate or estradiol benzoate. This in vitro assay allows the measurement of circulating bioactive FSH and provides a convenient tool to advance studies on the role of FSH in the neuroendocrine control of gonadal maturation and reproductive cycles.
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PMID:Sensitive in vitro bioassay for the measurement of serum follicle-stimulating hormone. 393 96

Approximately 60% of the total particulate phosphodiesterase activity occurring in cardiac tissue was associated with the nuclear fraction. Cyclic GMP phosphodiesterase activity of the purified cardiac nuclear fraction was selectively inhibited by trifluoperazine (I50 = 19 microM) with negligible inhibition (less than 15%) of cyclic AMP phosphodiesterase activity. Inhibition of cyclic GMP phosphodiesterase by trifluoperazine was calcium-dependent and suppressed by ethylene glycol bis (beta-aminoethyl ether)N, N, N', N'-tetraacetic acid (EGTA). The inhibitory response of both phosphodiesterases to papaverine was similar in the presence of calcium. However, in the presence of EGTA, papaverine inhibition of cyclic GMP but not cyclic AMP phosphodiesterase was reduced significantly. Calmodulin (1-5 micrograms/ml) readily reversed the inhibition by 25 microM trifluoperazine of membraneous cyclic GMP phosphodiesterase, but had no effect on inhibition by papaverine. With imidazolidinone analogues (Ro 7-2956 and Ro 20-1724), EGTA enhanced the inhibition of cyclic GMP phosphodiesterase without significantly altering the inhibition of cyclic AMP phosphodiesterase. Inhibition of cyclic AMP of cyclic GMP phosphodiesterase activity by 1-methyl-3-isobutylxanthine, quinidine, or compound SQ 20,009 was not affected appreciably by calcium or EGTA. The selective inhibitory action of certain pharmacological agents on phosphodiesterases of cardiac nuclear fraction and the modulation of the inhibitory response by calcium suggest an intrinsic and predominant association of calmodulin with cyclic GMP phosphodiesterase activity of these membranes.
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PMID:Selective inhibition of cyclic AMP and cyclic GMP phosphodiesterases of cardiac nuclear fraction. 617 20


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