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)

Rat brain microsomes have the capacity to liberate radioactive free aldehydes from 1-[1-14C]alk-1'-enyl-sn-glycero-3-phosphoethanolamine (lysoplasmalogen). Glycerophosphoethanolamine was found using 1-alk-1'-enyl-sn-glycero-3-phospho-[3H]ethanolamine. The ratio of both products released by lysoplasmalogenase action was 1:1. Another enzymic activity could be demonstrated, which hydrolyzes lysoplasmalogen at the hydrophilic part of the molecule, a lysophospholipid phosphodiesterase. Thus, 1-[1-14C]alk-1'-enylglycerol was detected as well as [3H]ethanolamine, again in a molar ratio, from the respective labeled substrates. This enzyme possesses nearly the same affinity toward the substrate as lysoplasmalogenase. Whereas the lysophospholipid phosphodiesterase is totally inhibited in the presence of NaF or EDTA, lysoplasmalogenase activity is not affected by these reagents. 1-[1-14C]Alk-1'-enylglycerol acts also as substrate for lysoplasmalogenase, which liberates radioactive aldehydes at the same rate as from lysoplasmalogen. Because the apparent Km and Vmax values are nearly identical for both substrates, the enzyme activities are inhibited in the same way, and the pH optimum is about 7.2 in both cases, it is concluded that both substrates were attacked by the same enzyme. The enzyme does not differentiate between a substrate substituted at the sn-3 position of glycerol and one that is not. It requires only a free OH group at the sn-2 position. Phosphoethanolamine phosphatase activity was also determined under our experimental conditions.
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PMID:Alkenylhydrolase: a microsomal enzyme activity in rat brain. 391 89

Calcium-tolerant myocytes were isolated from rat hearts. Isoproterenol produced a dose-dependent increase in glycerol output (lipolysis) that could be blocked by propranolol. The presence of glucose in the incubation medium enhanced the release of glycerol from myocytes but had no effect on the decline in triacylglycerol content. No incorporation of radioactivity from [U-14C]glucose into glycerol could be detected. In incubations with isoproterenol, there was a stoichiometric relationship between the glycerol output and the decrease in triacylglycerol levels. The addition of the phosphodiesterase inhibitor 1-methyl-3-isobutylxanthine resulted in an increase in the basal glycerol output and an enhancement of the isoproterenol-stimulated lipolytic rate. Forskolin and 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate also produced a concentration-dependent stimulation of lipolysis in myocytes. Therefore, lipolysis in isolated myocytes must be regulated by adenosine 3',5'-cyclic monophosphate-dependent mechanisms. These results demonstrate that lipolysis can be observed in myocardial cells and that the lipolytic response to isoproterenol cannot be secondary to a physiological (inotropic) response since these myocyte preparations are quiescent.
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PMID:Stimulation of lipolysis in rat heart myocytes by isoproterenol. 403 87

Homogenates of Musca domestica (housefly) larvae contain glycerophosphodiesterase activity, which is found in the supernatant fluid after centrifugation at 88,000 g. The phosphodiesterase is inhibited by EDTA and is stimulated by Mg(2+), Ni(2+), Co(2+), and Mn(2+). The pH optimum is 7.2. The enzyme is stable to heating at 50 degrees C for 15 min and is insensitive to sulfhydryl inhibitors. Glycerophosphoryl diesters of choline, ethanolamine, inositol, serine, glycerol, and beta-methylcholine are hydrolyzed to the common product, l-alpha-glycerophosphate, and the appropriate free alcohol. The rate of glycerophosphorylcholine hydrolysis is 70% greater than the rate of hydrolysis of the other glycerophosphodiesters. Apparent K(m) values for glycerophosphorylcholine, glycerophosphorylethanolamine, and glycerophosphoryl-beta-methylcholine are 2-4 x 10(-4) m, and for glycerophosphorylinositol, 2 x 10(-3) m. Competitive studies using various pairs of substrates, as well as the exchange of free choline into both glycerophosphorylcholine and glycerophosphorylinositol, suggest that a single enzyme cleaves all substrates. Product inhibition and reversal of the reaction were not detected. Choline, but not l-alpha-glycerophosphate, exchanges into glycerophosphorylcholine and glycerophosphorylinositol.
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PMID:Characterization of glycerophosphorylcholine, -ethanolamine, -serine, -inositol, and -glycerol hydrolytic activity in housefly larvae. 433 55

Cardiolipin (CL) synthetase from Staphylococcus aureus catalyzes the complete conversion of two molecules of phosphatidylglycerol (PG) to one molecule of CL and one molecule of glycerol. The fatty acids and phosphates of the two PG molecules can be quantitatively recovered in the CL. The enzyme is membrane-bound, shows a linear relationship with the product formed between 10 and 125 mug of membrane protein, has a pH optimum at 4.4, a temperature optimum between 37 and 45 C, a K(m) for PG of 2.1 x 10(-4)m, a V(max) of 200 nmoles of CL per min per mg of membrane protein, and does not require monovalent or divalent metals for activity. The enzyme has no nucleotide requirement and is not affected by prolonged dialysis, and treatment of the enzyme with charcoal has no effect on its activity. The enzyme has no phosphomonoesterase or phosphodiesterase activity, does not act on CL, is specific for PG, and CL and glycerol are the sole products of its activity. Other lipids do not stimulate or inhibit its activity. The enzyme is inhibited by organic solvents and some detergents. There is sufficient CL synthetase activity to account for CL synthesis during exponential growth. Inhibition of CL hydrolysis during growth results in an increase in CL that is balanced by a loss of PG. The activity of CL synthetase is not affected by cytidine diphosphate diglyceride but is inhibited competitively by the product, CL.
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PMID:Biosynthesis of cardiolipin from phosphatidylglycerol in Staphylococcus aureus. 505 54

1. The purification of a nuclease from rat-liver mitochondria is described. The mitochondria are rendered soluble by treatment with Triton X-100 and, after fractionation with ammonium sulphate and acetone, the active fraction is further purified by chromatography on DEAE-cellulose and Sephadex G-75 to give a purification of over 700-fold. 2. The purified enzyme was only very slightly contaminated with deoxyribonuclease II, phosphodiesterase and phosphomonoesterase. The individual activities of these enzymes did not exceed 0.1% of the activity of the liver nuclease. 3. The purified enzyme attacked RNA more rapidly than denatured DNA and hydrolysed native DNA more slowly than denatured DNA. 4. There is some evidence to suggest that the nucleolytic activity of the purified preparation towards native DNA, denatured DNA and RNA is associated with a single protein. 5. The enzyme is relatively labile but is stabilized in the presence of 20% (w/v) glycerol or 10mm-2-mercaptoethanol.
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PMID:The purification from rat liver of a nuclease hydrolysing ribonucleic acid and deoxyribonucleic acid. 591 28

The physiological function of cyclic AMP (cAMP) phosphodiesterase in Salmonella typhimurium was investigated with strains which were isogenic except for the cpd locus. In crude broken-cell extracts the properties of the enzyme were found to be similar to those reported for Escherichia coli. The specific activity in the mutant was less than 1% that in the wild type. Rates of cAMP production in the mutant were as much as twice those observed in the wild type. The amount of cAMP accumulated when cells grew overnight with limiting glucose was 4.5-fold greater in the mutant than in the wild type. The intracellular concentration of cAMP in the two strains was measured directly, using four different techniques to wash the cells to remove extracellular cAMP. The cAMP level in the cpd strain was only 25% greater than in the wild type. The functional concentration of the cAMP receptor protein-cAMP complex was estimated indirectly from the specific activity of beta-galactosidase in the two strains after introducing F'lac. When cells were grown with carbon sources permitting synthesis of different levels of cAMP, the specific activity of the enzyme was at most 25% greater in the cpd strain. The cpd strain was more sensitive to the effects of exogenous cAMP. Exogenous cAMP relieved both permanent and transient catabolite repression of the lac operon at lower concentrations in the cpd strain than in the wild type. When cells grew with glucose, glycerol, or ribose, exogenous cAMP inhibited growth of the mutant strain more than the wild type.
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PMID:Cyclic AMP phosphodiesterase in Salmonella typhimurium: characteristics and physiological function. 609 95

Glutamine synthetase from a Gram-positive acid-fast bacterium, Mycobacterium smegmatis, was purified to homogeneity from cells grown with glycerol-bouillon medium. Electron micrographs of the enzyme revealed a dodecameric arrangement of its subunits in two superimposed hexagonal rings, similar to the structure of glutamine synthetase of Escherichia coli. Disc electrophoresis in the presence of sodium dodecyl sulfate indicated a subunit molecular weight of 56,000. The sedimentation coefficient of the native enzyme was estimated to be 19.4S by ultracentrifugation in a sucrose gradient. Like the E. coli enzyme, the glutamine synthetase from M. smegmatis is regulated by adenylylation/deadenylylation. This conclusion was based on studies of the effect of snake venom phosphodiesterase treatment on the catalytic and spectral properties of the isolated enzyme. The AMP released from the enzyme by the phosphodiesterase was identified by thin-layer chromatography. Despite the structural similarity of both enzymes, striking differences were found between the catalytic properties of M. smegmatis and E. coli glutamine synthetases. The divalent cation specificity of the M. smegmatis enzyme was not altered by adenylylation of the enzyme, and deadenylylation of the enzyme caused a significant increase in the specific activities for both biosynthetic and transfer reactions with either Mg2+ or Mn2+.
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PMID:Regulation of Mycobacterium smegmatis glutamine synthetase by adenylylation. 614 40

The ability of hormones to activate responses in a variety of tissues decreases with age. The mechanism(s) responsible for these alterations are unclear. We have confirmed that the ability of a beta-adrenergic receptor agonist to activate lipolysis in isolated rat adipocytes decreases with age. Maximum response to isoproterenol was greater in 2-mo-old rats (600 +/- 30 nmol of glycerol released/10(5) cells per h) than 12-mo-old rats (250 +/- 25 nmol/10(5) cells per h), P less than 0.001. Similarly, ACTH is less effective in activating lipolysis in the adipocytes from the older rats. However, the cAMP analogue 8-(4-chlorophenothio)adenosine 3',5'-monophosphate cyclic activated lipolysis equally in the two groups, suggesting that the deficit in adipocytes from the older rats was proximal to cAMP-dependent protein kinase activation. Both isoproterenol and ACTH were significantly less effective in promoting cAMP accumulation in adipocytes isolated from 12-mo-old rats. There was no difference in phosphodiesterase activity of the adipocytes between the two groups. beta-Adrenergic receptors were measured using the antagonist radioligand [125I]cyanopindolol. The number of beta-adrenergic receptors was actually increased in the adipocytes from 12-mo-old rats (26,000 +/- 2,600 receptors/cell) compared with cells from 2-mo-old rats (7,200 +/- 1,300 receptors/cell). The results suggest that diminished cAMP production is responsible for the diminished lipolytic response in the adipocytes of older rats. The mechanism responsible for this change is uncertain but cannot be explained by a loss in beta-adrenergic receptors.
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PMID:Age-related decrement in hormone-stimulated lipolysis. 615 Jun 43

Changes of lipid, free fatty acid, protein, DNA, and RNA content in proximal and distal segments of regenerating sciatic nerve, from 14 to 120 days after crush, were determined. During the early stage of Wallerian degeneration, a marked decrease of phospholipid, cerebroside and sulfatide content and, in contrast, a marked increase of protein, DNA, RNA, and free fatty acid content, in the distal segment of crushed nerve compared to control, was observed. A gradual increase of phospholipid, cerebroside, and sulfatide levels, approaching normal values, and a gradual slope in the increase of protein, DNA, RNA, and free fatty acid levels over the ensuing time periods of regeneration was seen. Total cholesterol content was relatively constant during regeneration, slightly increasing at day 120. The activity of 2', 3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) of myelin fraction purified from distal segment of regenerating sciatic nerve showed a significant increase in the 30-120 day regenerating period. A marked increase of the incorporation of [2-3H]glycerol and of [Me-14C]choline into myelin lipids of distal segment of regenerating nerve, was found. Labeling of myelin lipids with [3H]oleic acid (injected intravenously seven days before crush) support the evidence that a similar pattern of degeneration exists between two different types of trauma, i.e. nerve crush or cut. The findings suggest that, in the distal segment of crushed nerve, the lipid content as well as the myelin lipid synthesis increase as the regeneration period proceeds.
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PMID:Myelination of regenerating sciatic nerve of the rat: lipid components and synthesis of myelin lipids. 619 98

Isolated hepatocytes and isolated adipocytes incubated in the absence of added calcium ions respond to insulin with a decrease in tissue cyclic AMP levels, and an increase in low Km phosphodiesterase activity. Isolated hepatocytes also showed a diminution of glucagon stimulated glucose output in response to insulin, while adipocytes responded with increased rates of glucose oxidation, lipid synthesis and decreased glycerol output. These responses to insulin are the same as those seen when the cells are incubated in buffers containing physiological concentrations of calcium ions. When extracellular concentrations of calcium ions were made extremely low by using either gelatine or albumin which had been pretreated to remove calcium, and/or the incubation buffers contained EGTA, both the hepatocytes and adipocytes continued to respond to insulin. These results suggest that extracellular calcium ions are not required for insulin action.
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PMID:Is extracellular calcium required for insulin action? 625 18


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