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) A system is described for studying the short-term effects of agents on proinsulin synthesis in vitro, as measured by the incorporation of [3H]leucine into isolated proinsulin. (2) Of the agents tested, glucose has the most marked, and apparently earliest, effect on proinsulin synthesis. (3) The adenyl cyclase system participates in the regulation of proinsulin synthesis since exogenous cyclic AMP, glucagon, and caffeine are stimulatory. When cyclic AMP is added to the medium in the presence of glucose, it is the most potent agent acting on the adenyl cyclase-phosphodiesterase system. (4) The addition of NADPH to isolated rat islets inhibits proinsulin and Bulk Protein synthesis in vitro.
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PMID:Regulation of proinsulin synthesis in isolated rat islets. 0 29

(125)I-labelled asialo-fetuin, administered intravenously, rapidly accumulates in rat liver and the radioactivity is subsequently cleared from the liver within 60min. Plasma radioactivity reaches a minimum between 10 and 15 min after injection and rises slightly during the period of liver clearance. Free iodide is the only radioactive compound found in plasma during this latter period. Fractionation of rat liver at 5 and 13min after injection of (125)I-labelled asialo-fetuin supports the hypothesis that asialo-glycoprotein is taken into liver by pinocytosis after binding to the plasma membrane and is then hydrolysed by lysosomal enzymes. At 5min, radioactivity was concentrated 23-fold in a membrane fraction similarly enriched in phosphodiesterase I, a plasma-membrane marker enzyme, whereas at 13min the radioactivity appeared to be localized within lysosomes. Separation of three liver fractions (heavy mitochondrial, light mitochondrial and microsomal) on sucrose gradients revealed the presence of two populations of radioactive particles. One population banded in a region coincident with a lysosomal marker enzyme. The other, more abundant, population of radioactive particles had a density of 1.13 and contained some phosphodiesterase, but very little lysosomal enzyme. These latter particles appear to be pinocytotic vesicles produced after uptake of the asialo-fetuin bound by the plasma membrane. Lysosomal extracts extensively hydrolyse asialo-fetuin during incubation in vitro at pH4.7 and iodotyrosine is completely released from the iodinated glycoprotein. Protein digestion within lysosomes was demonstrated by incubating intact lysosomes containing (125)I-labelled asialo-fetuin in iso-osmotic sucrose, pH7.2. The radioactive hydrolysis product, iodotyrosine, readily passed through the lysosomal membrane and was found in the external medium. These results are not sufficient to account for the presence of free iodide in plasma, but this was explained by the observation that iodotyrosines are deiodinated by microsomal enzymes in the presence of NADPH.
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PMID:Glycoprotein catabolism in rat liver: Lysosomal digestion of iodinated asialo-fetuin. 5 34

The CD (circular dichroism) and CPL (circular polarization of luminescence) spectra of NADPH in aqueous solution were studied and found to be markedly different. The spectra were not affected by cleavage of the coenzyme molecule with phosphodiesterase. The differences are thus not due to the existence of extended and folded conformations of NADPH and it is concluded that they originate in excited state conformational changes of the nicotinamide--ribose fragment. Opposite signs of both the CD and CPL spectra were observed for NADH bound to horse liver alcohol dehydrogenase and to beef heart lactate dehydrogenase indicating structural differences between the nicotinamide binding sites. The binding of substrate analogues to enzyme--coenzyme complexes did not affect the CD spectra and hence no significant conformational changes are induced upon formation of the ternary complexes. No changes in the CPL spectrum of NADH bound to lactate dehydrogenase were observed upon adding oxalate to form the ternary complex. Marked differences were found between the CPL spectra of binary and ternary complexes with liver alcohol dehydrogenase, while the CD spectra of these complexes were identical. It is concluded that a conformational change of the excited NADH molecule occurs in the binary but not in the ternary complex involving LADH, thus indicating an increased rigidity of the latter complex.
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PMID:Circular dichroism and circular polarization of luminescence of reduced nicotinamide adenine dinucleotide in solution and bound to dehydrogenases. 20 11

A procedure for the isolation of plasma membranes from protoplasts of suspension-cultured soybean is described. Protoplasts were prepared by enzymic digestion of the cell wall and the plasma membrane was labelled with radioactive diazotized sulphanilic acid. The membrane systems from broken protoplasts were separated by continuous isopycnic sucrose gradient centrifugation. Radioactivity was localized in a band possessing a buoyant density of 1-14 g ml-1. The activities of NADPH- and NADH-cytochrome c reductase, fumarase, Mg2+-ATPase, IDPase and acid phosphodiesterase in the various regions of the density gradient were determined. A plasma membrane fraction was selected which was relatively uncontaminated with membranes derived from endoplasmic reticulum, tonoplasts and mitochondria. The results indicated that Mg2+-ATPase and possibly acid phosphodiesterase were associated with the plasma membrane.
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PMID:The isolation of plasma membrane from protoplasts of soybean suspension cultures. 56 Oct 89

"Paralytic tremor" (pt) rabbit mutant is characterized by a severe hypomyelination of the CNS, however, it is not defined if the defect in myelinogenesis is an "assembly" or "synthesis" type. In this study, we have compared the general metabolic and biosynthetic properties of the myelinating mutant brain with unaffected controls of the same age. In the brain slices of 4 wk old "pt" rabbits the incorporation of U-[14C]glucose, 6-[3H] galactose, and U-[14C] leucine into macromolecules (total lipids and proteins, galactolipids, and myelin basic protein) was substantially elevated. In isolated myelin fraction, the total reduction of the radioactivity was followed by the increased specific activity of all examined macromolecules. The myelin to homogenate specific activity ratio was similar in control and "pt" rabbits. Distribution of the label and myelin marker, cyclic nucleotide 3'-phosphodiesterase (CNP-ase) among the membranous fractions suggests the partial inhibition of myelin formation in "pt" rabbits on the step of premyelin, unilamellar membranes. 14CO2 yields derived from differently labeled glucose were used for the evaluation of the basal oxidative metabolism in "pt" brain slices. 14CO2 production from U-[14C] glucose was normal. The depolarization of the slices by 50 mM K+ stimulated glucose oxidation to a higher extent in "pt" than in control. Hexose monophosphate pathway (HMP), the route providing much of NADPH required for lipid biosynthesis, did not change significantly by mutation. The activity of glucose 6-phosphate dehydrogenase (Glc-6-P DH), an oligodendroglia enriched, HMP connected enzyme, was slightly lower in "pt" homogenates by 13-17%, whereas CNP-ase was lowered more than 30% in the same samples. All this data suggest that the capacity for the synthesis of myelin constituents is well preserved in the mutant brain and the impairment of myelogenesis is probably caused by increased elimination of already synthesized, myelin-related components.
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PMID:Metabolic studies on dysmyelinating mutant "pt" rabbit brain in vitro. 284 Jun 12

The subcellular distribution of the 3H--2,6-dimethyl-3,5-dicarbomethoxy-4(2-isothiocyano) phenyl-1,4-dihydropyridine (DPSCN) binding to guinea-pig ileal smooth muscle was studied by subcellular fractionation. Initial experiments on subcellular fractionation of 3H-DPSCN-labelled tissues by differential centrifugation showed that there was an excellent correlation between the levels of the label present in a fraction and the plasma membrane marker phosphodiesterase I (r = 0.98) but not between the label and the putative endoplasmic reticulum marker NADPH: cytochrome-c-reductase (r = 0.56) or the inner mitochondrial marker cytochrome-c-oxidase (r = 0.36). Centrifugation of the microsomes on a continuous sucrose density gradient showed an excellent correlation of the migration of the label with phosphodiesterase I activity (r = 0.93) but not with the activities of NADPH: cytochrome-c-reductase (r = 0.66) or cytochrome-c-oxidase (r = 0.44). Treatment of microsomes with digitonin (1 mg/ml) followed by centrifugation on continuous sucrose density gradients increased the weighted mean densities of the phosphodiesterase activity (plasma membrane marker) and the labelling by similar magnitudes (0.04 to 0.06 g/ml). The weighted mean densities of NADPH: cytochrome-c-reductase and the cytochrome-c-oxidase were not altered significantly. It is concluded that in the guinea-pig ileal smooth muscle, DPSCN labels the plasma membrane specifically.
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PMID:Subcellular distribution of dihydropyridine isothiocyanate binding in guinea-pig ileal smooth muscle. 298 69

A plasma membrane fraction from bovine carotid arteries has been isolated by extraction of a crude microsomal fraction with a low-ionic-strength buffer containing ATP and Ca2+. This step was followed by sucrose-density-gradient centrifugation in the presence of 0.6 M KCl. The plasma membrane vesicles were enriched 60- to 80-fold in Na+-K+-adenosinetriphosphatase, 5'-nucleotidase, and phosphodiesterase I activities. The final yields of these marker enzymes were 12-18% of the total activities in the postnuclear supernatant, and the protein yield was 100-120 micrograms/g wet wt of carotid arteries. Contamination of the plasma membrane fraction by mitochondria and sarcoplasmic reticulum was low as judged by low activities of succinate--cytochrome-c reductase and NADPH--cytochrome-c reductase, respectively. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and immunoprecipitation with smooth muscle-specific actin antibodies showed that the plasma membrane fraction was substantially free from myosin and actin contamination. The plasma membrane vesicles accumulated Ca2+ in the presence of ATP, and the accumulation was increased by calmodulin. Ca2+ accumulated in the presence or absence of calmodulin could be released almost completely from the vesicles by the addition of the Ca2+ ionophore A23187 but not by ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid, indicating that Ca2+ uptake in the presence of ATP is intravesicular. The effects of phosphate and oxalate on Ca2+ uptake in the plasma membranes were different from one another. Phosphate increased Ca2+ uptake in a concentration- and time-dependent manner, and the increase in Ca2+ uptake could be observed as early as 1 min. On the other hand, oxalate at concentrations up to 5 mM did not increase Ca2+ uptake significantly during the 30-min incubation. These plasma membranes can prove useful for the study of ion transport across plasma membranes, hormone binding, characterization of calcium channels, and preparation of antibodies against plasma membrane proteins.
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PMID:Isolation and characterization of plasma membranes from bovine carotid arteries. 300 86

In order to resolve discrepancies in the literature concerning the subcellular localization of NADPH oxidase, we disrupted human neutrophils by nitrogen cavitation and fractionated the subcellular organelles on a discontinuous sucrose density gradient. The lightest fraction was 20- to 40-fold enriched for plasma membranes as determined by the marker enzymes alkaline phosphatase and phosphodiesterase I as well as by the ratio of lipid phosphorus to protein. There was a significant decrease in the specific activities of the granule markers myeloperoxidase, lysozyme, and beta-glucuronidase. An intermediate fraction was enriched in membrane markers but not to the extent the lightest fraction was enriched. This fraction contained more granular contamination, as shown by the marker enzymes. In contrast, the densest bands of the gradient were enriched for granule markers with little contamination by plasma membrane. Superoxide generation and NADP formation were primarily associated with the two membrane-enriched fractions from polymorphonuclear leukocytes stimulated with phorbol myristate acetate. The NADP formation associated with a dense granule fraction observed previously in our laboratory was probably due to a cyanide-stimulated oxidation of NADPH by myeloperoxidase.
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PMID:Co-localization of superoxide generation and NADP formation in plasma membrane fractions from human neutrophils. 609 76

The oxalate-stimulated and -independent components of the ATP-dependent azide insensitive Ca-uptake by rat vas deferens smooth muscle microsomes differ in the following properties: (a) 5, 5'-disulfonate stilbene (DIDS) and digitonin inhibited the oxalate-independent Ca-uptake more strongly than the oxalate-stimulated component; (b) phosphatidylserine inhibited the oxalate-stimulated Ca-uptake and had no significant effect on the oxalate-independent uptake and (c) digitonin treatment of microsomes changed the density distributions of the two modes differentially. The untreated microsomes gave two Ca-uptake peaks on sucrose density gradients: one at density 1.130 +/- 0.010 g/ml and the other at 1.214 +/- 0.005 g/ml. Digitonin treatment shifted the distribution of the lower density peak to slightly higher density for the oxalate-independent Ca-uptake but not for the oxalate-stimulated Ca-uptake. Distribution of phosphodiesterase I was also shifted to higher densities while distributions of the higher density Ca-uptake peak, NADPH: cytochrome c reductase and of cytochrome c oxidase were not significantly altered. Thus clearly the oxalate-stimulated and the oxalate-independent Ca-uptake in rat vas deferens smooth muscle microsomes show several differences but it is unknown whether the differences are due to the existence of two distinct Ca-pump proteins or due to different microenvironment of the same protein resulting from membrane heterogeneity.
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PMID:ATP-dependent Ca-uptake by rat vas deferens smooth muscle microsomes: properties of oxalate stimulated and oxalate-independent Ca-uptake. 672 23

The relationship between adenylate cyclase activity in the synaptic membrane fraction (M1) of rat brain and lipid peroxidation of these membranes was examined. In the presence of 5 mM dithiothreitol (DTT), 1 to 10 microM Fe/+ activated adenylate cyclase 2- to 4-fold. Of several metal ions, Fe2+ was the most effective. Other enzymes in M1, such as Mg2+-ATPase, (Na+-K+)-ATPase, 5'-nucleotidase, acetylcholinesterase, and phosphodiesterase, were not activated by Fe2+ plus DTT. Activation of adenylate cyclase by Fe2+ plus DTT was accompanied by production of malondialdehyde, a product of lipid peroxidation. Formation of malondialdehyde was completely parallel with enzyme activation. Ascorbic acid or a NADPH system also stimulated enzyme activity and caused lipid peroxidation. Activation of the enzyme and lipid peroxidation induced by Fe2+ plus DTT, ascorbic acid, or NADPH was completely prevented by simultaneous addition of N,N'-diphenyl-p-phenylenediamine, an inhibitor of lipid peroxidation. This inhibitor also prevented the decrease in turbidity of the enzyme preparation induced by Fe2+ plus DTT. The stimulatory effects of NaF, guanylyl-5'-imidodiphosphate and calmodulin, respectively, and that of Fe2+ plus DTT on the enzyme activity were additive. Activation of adenylate cyclase by Fe2+ plus DTT was only observed in brain synaptic membranes, not in erythrocyte ghosts, liver plasma membranes, or cardiac sarcolemma. These results indicate that lipid peroxidation of synaptic membranes was accompanied by specific stimulation of adenylate cyclase activity.
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PMID:Activation of adenylate cyclase of rat brain by lipid peroxidation. 721 51


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