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

---

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

1. The effects of changes in the cytoplasmic [NADH]/[NAD+] ratio on the efficacy of glucagon to alter rates of metabolism in isolated rat hepatocytes were examined. 2. Under reduced conditions (with 10mM-lactate), 10nM-glucagon stimulated both gluconeogenesis and urea synthesis in isolated hepatocytes from 48h-starved rats; under oxidized conditions (with 10mM-pyruvate), 10nM-glucagon had no effect on either of these rates. 3. The ability of glucagon to alter the concentration of 3':5'-cyclic AMP and the rates of glucose output, glycogen breakdown and glycolysis in cells from fed rats were each affected by a change in the extracellular [lactate]/[pyruvate] ratio; minimal effects of glucagon occurred at low [lactate]/[pyruvate] ratios. 4. Dose-response curves for glucagon-mediated changes in cyclic AMP concentration and glucose output indicated that under oxidized conditions the ability of glucagon to alter each parameter was decreased without affecting the concentration of hormone at which half-maximal effects occurred. 5. The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (0.05 mM) significantly reversed the inhibitory effects of pyruvate on glucagon-stimulated glucose output. 6. For exogenously added cyclic [3H]AMP(0.1 mM), oxidized conditions decreased the stimulatory effect on glucose output as well as the intracellular concentration of cyclic AMP attained, but did not alter the amount of cyclic [3H]AMP taken up. 7. The effects of lactate, pyruvate, NAD+ and NADH on cyclic AMP phosphodiesterase activities of rat hepatocytes were examined. 8. NADH (0.01--1 MM) inhibited the low-Km enzyme, particularly that which was associated with the plasma membrane. 9. The inhibition of membrane-bound cyclic AMP phosphodiesterase by NADH was specific, reversible and resulted in a decrease in the maximal velocity of the enzyme. 10. It is proposed that regulation of the membrane-bound low-Km cyclic AMP phosphodiesterase by nicotinamide nucleotides provides the molecular basis for the effect of redox state on the hormonal control of hepatocyte metabolism by glucagon.
...
PMID:Responsiveness to glucagon by isolated rat hepatocytes controlled by the redox state of the cytosolic nicotinamide--adenine dinucleotide couple acting on adenosine 3':5'-cyclic monophosphate phosphodiesterase. 21 54

Parathyroid hormone (PTH) and glucagon increase the urinary fractional excretion of phosphate, but insulin administration is associated with a decreased fractional excretion of phosphate. It was the purpose of this study to determine whether insulin will antagonize the effects of PTH and glucagon on cAMP levels and protein kinase activation of rat renal cortex. In situ incubation studies were performed on rat renal cortical slices exposed to insulin, PTH, and glucagon. Insulin alone did not affect the tissue cAMP and cGMP levels or the state of protein kinase activation. Preincubation of slices with insulin, however, did significantly inhibit increases in protein kinase activation induced by both PTH and glucagon. Insulin also significantly inhibited PTH-stimulated increases in tissue cAMP levels, but did not blunt the elevations of cAMP levels induced by glucagon. Insulin (10(-9) M) had no effect on either the in vitro activity of adenylate cyclase, basal or PTH-stimulated, or on the activities of low Km cytosolic or membrane-bound cAMP phosphodiesterase. The data show that insulin antagonizes activation of protein kinase by both PTH and glucagon in renal cortex. Separate mechanisms are probably involved for PTH and glucagon interaction. The antiphosphaturic effect of insulin in vivo may result in part from this antagonism at the cellular level.
...
PMID:Insulin inhibition of hormone-stimulated protein kinase systems of rat renal cortex. 22 Aug 84

The hydrolysis of membrane-bound phosphatidylinositol in rat liver microsomal fraction by the soluble phosphatidylinositol phosphodiesterase from rat brain was markedly stimulated by oleic acid or arachidonic acid. The stimulation did not require added calcium, although it was abolished by EDTA. Lysophosphatidylcholine also totally suppressed the stimulation. A possible role for the fatty acid content of a membrane in controlling phosphatidylinositol turnover is suggested.
...
PMID:Fatty acid stimulation of membrane phosphatidylinositol hydrolysis by brain phosphatidylinositol phosphodiesterase. 22 Sep 68

Contact-inhibited 3T3 mouse fibroblast cells, in contrast to logarithmically growing 3T3 cells and SV-3T3 transformed cells, have increased levels of plasma membrane-bound phosphodiesterase (oligonucleotidase, E.C.3.1.4.19; nucleotide pyrophosphatase, E.C. 3.6.1.9) activity. The increase in enzyme, recorded as increased specific activity, is reversible, as evidenced by the return to normal values following dilution of confluent 3T2 cells and re-initiation of growth. Increased enzyme activity is induced again when the cells regain the confluent state. Transformed SV-3T3 cells can be induced to mimic the contact inhibited state, including increased plasma membrane phosphodiesterase activity, by exposure to a combination of: (i) agents that are known to induce increased intracellular cAMP levels and (ii) additions of purified 3T3 or SV-3T3 plasma membranes. Additions of either alone fails to induce the increase in membrane phosphodiesterase activity, although each alone can significantly suppress cell growth, as measured by incorporation of 3H amino acids. We suggest that the elevation of plasma membrane phosphodiesterase activity may serve as a measure of conversion to the contact-inhibited state in both normal cells and phenotypically reverted transformed cells.
...
PMID:Increase in plasma membrane phosphodiesterase activity in contact-inhibited 3T3 cells and in phenotypically reverted SV-3T3 cells. 22 43

Studies were carried out to characterize the cyclic nucleotide phosphodiesterase from rat calvaria. 25-40% of the total enzyme activity was membrane-bound. pH, magnesium, and temperature requirements conformed closely to those established for phosphodiesterase from other tissues. Kinetic evidence was found for dual enzyme activities with different substrate affinities for both the particulate and soluble enzyme. Apparent Kms for the soluble enzyme (3.5 times 10-6 and 2.5 times 10-5M) approximated those for the particulate enzyme (5.7 times 10-6 and 2.5 times 10-5M). L-Thyroxine, 10-5M, inhibited competitively the low- and high-Km enzymes from both the particulate and soluble fractions (Ki equals 1.7 times 10-5M). T4 was more potent an inhibitor than T3 with all enzyme fractions, but this relationship could be altered by adding protein to the incubation mixtures. Tests of diverse thyroid hormone analogues showed that 1) T4 and its derivatives were more potent than T3 and its analogues; 2) acetic and propionic acid derivatives were more potent than the thyronines; 3) "reverse T3," an antagonist of some T3 actions, also inhibited phosphodiesterase. These effects were not attributable to chelation, and were not duplicated by iodide or by other physiologically inactive thyroid hormone analogues.
...
PMID:Cyclic nucleotide phosphodiesterase from bone: characterization of the enzyme and studies of inhibition by thyroid hormones. 23 82

Mitoplasts from rat liver mitochondria and ETPH particles from beef heart mitochondria were reacted with TNBS and FDNB in sucrose-mannitol-bicarbonate buffer pH 8.2 (BUFFER A) and in sodium chloride-bicarbonate buffer pH 8.5 (buffer B). Mitoplasts and ETPH particles are more stable in buffer A and very little hydrolysis of phospholipids occurs during the reaction period. In this buffer TNBS reacts to a lesser extent with phosphatidylethanolamine (PE) than does FDNB. The data suggests that with mitoplasts 65% of the total PE is localized on the outer surface of the membrane. With mitoplasts the labeling of membrane proteins is much more extensive with FDNB and suggests that 66% of the proteins are localized on the inner membrane surface. Thus a dual type of asymmetry occurs in the mitoplast membrane with more PE localized on the outer surface and more protein localized on the inner surface. In buffer B, extensive degradation of the dinitrophenylated and trinitrophenylated PE and LPE occurs to yield DNP-GPE and TNP-GPE respectively. DNP-GPE and TNP-GPE are degraded by a phosphodiesterase to DNP-ethanolamine and TNP-ethanolamine. When ETPH particles are labeled with TNBS and FDNB, washed, and incubated in buffer A and buffer B, a resynthesis of TNP-PE and DNP-PE occurs in buffer A by acylation of TNP-LPE whereas DNP-PE continues to be formed, primarily from DNP-GPE. These studies provide evidence for an asymmetric arrangement of PE in the inner mitochondrial membrane and demonstrate the presence of membrane-bound phospholipases which act on dinitrophenylated and trinitrophenylated amino-phospholipids. A membrane bound phosphodiesterase is also present which degrades dinitrophenylated or trinitrophenylated GPE. The degradative reactions prevail in bicarbonate-NaCl buffer B whereas acylation reactions prevail in sucrose-mannitol buffer A.
...
PMID:Reaction of amino-phospholipids of the inner mitochondrial membrane with fluorodinitrobenzene and trinitrobenzenesulfonate. 99 87

The binding of [125I]endothelin-1 (125I-ET-1) to membranes from whole rat brain, from individual brain regions, and derived from subcellular fractionation of whole rat brain was investigated. 125I-ET-1 binding to whole rat brain membranes was rapid, concentration-dependent, saturable, and characterized as irreversible because it was not displaced by unlabeled endothelin-1 (ET-1) and different concentrations of ligand produced, with time, a similar magnitude of binding. The maximum binding site capacity and second-order forward rate association constant of binding were 1,946 +/- 147 fm/mg protein and 5.53 +/- 1.72 x 10(6) M-1 s-1. Removal of either extramembranal calcium or membrane-bound calcium and calcium binding proteins did not affect the binding of 125I-ET-1 to whole rat brain membranes. The brain stem and cerebellum contained the highest levels of 125I-ET-1 binding sites, whereas the cerebral cortex, striatum, and hippocampus contained binding site levels three- to fourfold less. Subcellular fractionation of whole rat brain and subsequent analyses of the distribution of 125I-ET-1 binding demonstrated a twofold enrichment of binding sites in the synaptosomal fraction compared to the homogenate. The myelin fraction contained a similar density of binding sites compared to the homogenate, while the mitochondrial and microsomal fractions contained considerably less binding sites. The ribosomal fraction did not contain any 125I-ET-1 binding sites. The subcellular distribution of 125I-ET-1 binding sites did not correlate with the distribution of 5'-nucleotidase, cytochrome-C oxidase, phosphodiesterase, and alkaline phosphatase. Depletion of extracellular calcium increased 125I-ET-1 binding in the synaptosomal fraction but not in the myelin and mitochondrial fractions.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:Regional and subcellular distribution of [125I]endothelin binding sites in rat brain. 131 99

Treatment of membranes from guinea-pig peritoneal eosinophils with deoxycholate and NaCl solubilized greater than 95% of the particulate cyclic AMP-specific phosphodiesterase (PDE IV). Solubilized PDE IV was at least 10 times more potently inhibited by selective PDE IV inhibitors (e.g. rolipram, denbufylline) than bound enzyme. Vanadate/glutathione complex (V/GSH) activated membrane-bound PDE IV and also increased potencies of these same inhibitors by at least 10-fold. Neither solubilization nor V/GSH markedly influenced the inhibitory activities of non-selective inhibitors (e.g. trequinsin, dipyridamole). Inhibitor effects on solubilized PDE IV and cyclic AMP accumulation in intact cells were strongly correlated. These results suggest a biologically important site on eosinophil PDE IV which is concealed or partially concealed in freshly prepared membranes and is exposed by solubilization or V/GSH.
...
PMID:Effects of solubilization and vanadate/glutathione complex on inhibitor potencies against eosinophil cyclic AMP-specific phosphodiesterase. 132 25

cGMP-specific phosphodiesterase (PDE) of vertebrate retinal rod outer segments (ROS) is composed of two catalytic subunits (PDE alpha and PDE beta) and two identical inhibitory subunits (PDE gamma). Native PDE alpha beta gamma 2 is peripherally bound to the membranes of ROS discs. We studied quantitatively its partition between soluble and membrane-bound fractions in ROS homogenates. In the presence of its activator, the alpha-subunit of transducin loaded with a triphosphate guanine nucleotide (T alpha*), PDE displayed a greatly enhanced membrane binding. Neither the purified PDE gamma.T alpha* complex, nor the PDE alpha beta and PDE alpha beta gamma forms of active PDE, showed a membrane binding comparable to that of PDE alpha beta gamma 2 in the presence of T alpha*. The T alpha*-activated PDE is therefore an undissociated complex tightly bound to the ROS membranes. Using limited proteolysis, we showed that the membrane anchoring of the whole complex implies not only PDE (mainly by the C terminus of PDE beta) but also both termini of T alpha*. The membrane binding of the purified PDE alpha beta species was also enhanced in the presence of T alpha*; a direct link would therefore exist between the activator and the catalytic subunits. From this work emerges a plausible structural model of the T alpha*-activated PDE, with its internal interactions and its sites of anchoring into the ROS membrane.
...
PMID:The cGMP phosphodiesterase-transducin complex of retinal rods. Membrane binding and subunits interactions. 132 53

Lipolytic activity of fish (Hoplias malabaricus), toad (Bufo paracnemis), and snake (Philodryas patagoniensis) adipose tissue was investigated in vivo and in vitro. Catecholamines or glucagon did not affect the release of free fatty acids (FFA) by incubated fish and toad adipose tissue. Catecholamines also failed to activate snake adipose tissue lipolysis, which even decreased in the presence of epinephrine. However, glucagon stimulated both the lipolytic activity of reptilian tissue in vitro and the mobilization of FFA to plasma when administered to snakes in vivo. The release of FFA from incubated fish, amphibian, and reptilian adipose tissue increased markedly in the presence of cAMP or xanthine derivatives, inhibitors of phosphodiesterase. Forskolin or fluoride, activators of specific components of the adenylate cyclase system, strongly stimulated toad adipose tissue lipolysis. The data suggest that adipocyte triacylglycerol lipase of ectotherm vertebrates is activated by a cAMP-mediated phosphorylation and that the organization of the membrane-bound adenylate cyclase system is similar to that of mammals.
...
PMID:Control of adipose tissue lipolysis in ectotherm vertebrates. 132 67


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>

---