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)

Reaction of peroxides with 5-deazaflavin bound to glucose oxidase, lactate oxidase, or D-amino acid oxidase results in the formation of 5-deazaflavin 4a, 5-epoxide. The reaction of D-amino acid oxidase with m-chloroperoxybenzoate is an exception since the reagent reacts rapidly with the protein moiety to form m-chlorobenzoate which then binds noncovalently near the unmodified coenzyme. Epoxide bound to glucose oxidase is converted to deazaFAD X X in a reaction similar to that observed previously with oxynitrilase and glycolate oxidase. With lactate oxidase the epoxide is quite stable in the absence of light. With D-amino acid oxidase, denaturation of the protein is accompanied by the release of the epoxide into solution where it decomposes in a manner similar to that observed with model epoxide compounds at neutral pH. Reaction of deazaFAD X X with phosphodiesterase and alkaline phosphatase yields deazariboflavin X X. The same compound has been formed in model studies by exposing 5-deazariboflavin 4a,5-epoxide to alkaline conditions. Structural studies indicate that this reaction involves contraction of the pyrimidine ring to yield 4-ribityl-6,7-dimethyloxazolo[ 4,5-b ]quinolin-2(4H)-one. Model reaction studies are consistent with a mechanism initiated by alkaline hydrolysis of the pyrimidine ring at position 4 followed by two additional steps which proceed at neutral pH. A similar mechanism for the enzyme reactions appears likely since analogous intermediates are detected in the glycolate oxidase and the model reactions. The results suggest that position 4 of the coenzyme in oxynitrilase, glycolate oxidase, and glucose oxidase must be accessible to solvent and that the protein moiety must facilitate the initial hydrolysis of the pyrimidine ring since the enzyme reactions occur at neutral pH. Failure to observe formation of deazaFMN X X with lactate oxidase is attributed, at least in part, to the inaccessibility of the pyrimidine ring to solvent.
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PMID:Reaction of enzyme-bound 5-deazaflavin with peroxides. Pyrimidine ring contraction via an epoxide intermediate. 613 30

Pyrophosphate, p-nitrophenyl phosphate and a variety of pyrimidine and purine nucleotides are hydrolyzed by the solubilized membrane-bound enzymes of the brush border plasma membrane of Hymenolepis diminuta. The pH optima (or ranges) for hydrolysis of substrates are 8.0 (pyrophosphate), 8.8 (p-nitrophenyl phosphate), 8.4-8.9 (nucleoside monophosphates), and 7.1-8.1 (nucleoside triphosphates); all substrates, with the exception of nucleoside triphosphates, have a higher affinity for the solubilized enzyme at pH 7.4 than at their optimal pH for hydrolysis. ATP is degraded completely by the enzyme preparation to adenosine and inorganic phosphate, but since neither ADP nor ATP accumulate in the incubation medium it is not known whether ATP hydrolysis involves the sequential hydrolysis of terminal phosphate groups. Isoelectric focusing and various chromatographic procedures (gel permeation, ion-exchange and hydrophobic interaction chromatography) fail to separate the alkaline phosphatase, phosphodiesterase, 5'-nucleotidase, adenosine triphosphatase and ribonuclease activities associated with the solubilized membrane preparation. Additionally, inhibitor studies indicate that only a single enzyme with low substrate specificity is involved in the hydrolysis of nucleotides, p-nitrophenyl phosphate, pyrophosphate and hexose phosphate esters. Purines and pyrimidines and their nucleosides interact with the active site, and in some instances activity of the enzyme is stimulated by an unknown mechanism.
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PMID:Nucleotide hydrolysis by solubilized membrane-bound enzymes of the brush border plasma membrane of Hymenolepis diminuta. 613 88

Plasma membranes of vertebrate lens fiber cells contain large numbers of gap junctions that may provide pathways for metabolic cooperation. Characterization of fiber cell gap junctions is thus necessary to understand this function. In this study, plasma membrane fractions were isolated from bovine lens according to established techniques, but without urea, detergents, or proteolytic enzymes. Electron microscopy indicated that isolated plasma membranes with gap junctions form double-membrane vesicles, and gap junctions comprised approximately 35% of the total membrane area in the crude fraction. These vesicles were impermeable to cationized ferritin, suggesting that they were sealed, and may be useful for permeability studies. Treatment of the crude fraction with 2.5% beta-mercaptoethanol or dithiothreitol caused reversible separation of junctional membranes, suggesting that disulfide bonds may be important in maintaining gap junction structure. Fractions with varying proportions of gap junctions were isolated using linear sucrose density gradient centrifugation. The proportional area of gap junction membrane versus total membrane in the various fractions ranged from 10% to at least 51%. The following plasma membrane enzymes were assayed in all fractions: Mg++-ATPase, Ca++-ATPase, alkaline phosphatase, phosphodiesterase, 5'-nucleotidase, and Na+, K+-ATPase. There was no correlation between enzyme activity and gap junction enrichment. This suggests that these enzymes are not associated with fiber cell gap junctions.
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PMID:Biochemical and structural characterization of membrane fractions from bovine lens. 613 51

Four types of 1-beta-D-arabinofuranosylcytosine (ara-C) conjugates with poly-L-glutamic acid (PLGA) or poly-N5-(2-hydroxyethyl)-L-glutamine (PHEG) were prepared in an attempt to enhance the efficacy of the drug in simple dosage schedules. The conjugates were made by linking ara-C to the carboxyl groups of PLGA directly at N-4 of ara-C (ara-C:PLGA) or indirectly through the 2-aminoethylphosphoryl or 6-aminohexylphosphoryl side chain which had been introduced to C-5' of ara-C, 1-[5'-(2-aminoethylphosphoryl)-beta-D-arabinofuranosyl]cytosine: PLGA [araCMP(C2):PLGA and 1-[5'-(6-aminohexylphosphoryl)-beta-D-arabinofuranosyl]cytosine:++ +PLGA, respectively, or made by converting the remaining carboxyl groups in the PLGA conjugates to the 2-hydroxyethylamide groups [ara-C:PHEG, ara-CMP(C2):PHEG, 1-[5'-(6-aminohexylphosphoryl)-beta-D-arabinofuranosyl]cytosine:++ +PHEG]. Studies in vitro showed that the conjugates had decreased cytotoxicity against L1210 cells when compared with that of ara-C. Studies in vivo showed that all of the conjugates, except ara-CMP(C2):PLGA, had a greater antitumor activity than did ara-C in L1210 tumor-bearing BALB/c X DBA/2 F, (hereafter called CD2F1) mice (inoculum, 1 X 10(5) cells i.p. on Day 0) which were treated by a single i.p. injection of either the conjugates or the control ara-C on Day 1. The largest antitumor activity [increased life span (ILS) 170%] was observed with a dosage of 50 mg (equivalent ara-C per kg) of ara-C:PHEG. When CD2F1 mice which had been inoculated i.p. with 1 X 10(5) L1210 cells were treated with an i.p. injection of 12.5 or 25 mg (equivalent ara-C per kg) of ara-C:PHEG daily for 5 days starting from Day 1, 2 of 5 mice survived more than 42 days, and the ILS of the remaining mice was 153 and 184%. The injections of 3.2 mg (equivalent ara-C per kg) of ara-C:PHEG showed a moderate antitumor activity with an ILS of 113% which was similar to the ILS (119%) found when unconjugated ara-C (400 mg/kg) was used to treat tumor-bearing mice. In in vitro release experiments, ara-C was released slowly from ara-C:PLGA at pH 7.4, and ara-CMP(C2):PLGA was chemically stable but cleaved by phosphodiesterase, acid phosphatase, and alkaline phosphatase to give mainly 1-beta-D-arabinofuranosylcytosine 5'-monophosphate.
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PMID:Antitumor activity of 1-beta-D-arabinofuranosylcytosine conjugated with polyglutamic acid and its derivative. 619 62

ATP pyrophosphohydrolase was partially purified from fetal bovine epiphyseal cartilage. The purification was about 10- and 100-fold over the enzyme activities of matrix vesicle fraction and cell homogenate, respectively. The pyrophosphohydrolase and alkaline phosphatase were separated by a sequential application of Sepharose CL-6B and DEAE-cellulose column chromatographies. The purified enzyme migrated as a single band corresponding to the molecular weight of 230,000 in sodium dodecyl sulfate-polyacrylamide disc gel by electrophoresis. The enzyme absolutely required Zn2+ for its activity and appeared to bind Zn2+ strongly with an apparent affinity of p[Zn2+]0.5 = 13.4. The apparent Km for ATP was 0.18 mM. The enzyme was also reactive toward various nucleoside triphosphates including GTP, CTP, and UTP. In contrast, various phosphodiesters including RNA, UDP-glucose, NAD, and bis-p-nitrophenylphosphate were 5% or less as reactive as the nucleoside triphosphates. The pyrophosphohydrolase was inactive toward adenosine 3':5'-monophosphate or various phosphonates. UDP-glucose (1 mM), NAD (1 mM), or RNA (1 mg/ml) failed to inhibit the ATP pyrophosphohydrolase activity. These observations suggest that the ATP pyrophosphohydrolase of the cartilage is probably not a phosphodiesterase I. The matrix vesicle fraction, which probably also included some plasma membrane vesiculated during collagenase digestion, contained the highest specific activity of the enzyme as compared to other subcellular fractions of either epiphyseal or articular cartilage.
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PMID:Purification and partial characterization of ATP pyrophosphohydrolase from fetal bovine epiphyseal cartilage. 621 90

An analog of lysophosphatidylcholine (1-dodecyl-propanediol-3-phosphocholine) which does not impair membrane-bound enzymes was used for the induction of shedding of membrane vesicles from intact calf thymocytes. Without liberation of intracellular enzymes such as lactate dehydrogenase (EC 1.1.1.27) the shedded membranes contained 15--25% of the total activity of the plasma membrane enzymes alkaline phosphatase (EC 3.1.3.1), nucleotide pyrophosphatase (EC 3.1.4.1) and gamma-glutamyl transferase (EC 2.3.2.2). Membrane-free supernatants only exhibited trace activities of these enzymes. Without further purification, the specific enzyme activities in shedded membranes were of the same order of magnitude as in purified plasma membranes prepared after nitrogen cavitation of thymocytes. Small amounts of membrane vesicles which showed a different composition could be removed without detergent. These membranes exhibited a 3-fold lower specific activity of the gamma-glutamyl transferase while that of the alkaline phosphatase and nucleotide pyrophosphatase was similar as in detergent induced membrane vesicles. Distinct differences also were found in the protein pattern. The content of total cholesterol and phospholipid in vesicles shed spontaneously or after detergent treatment was nearly identical, however, significant differences were found in the fatty acid composition of the main phospholipids. The content of polyunsaturated fatty acids (linoleic and arachidonic acid) increased in the order: spontaneously shedded membranes, detergent induced vesicles, conventional purified plasma membranes. These results are discussed in terms of the heterogeneous composition of areas of the thymocyte plasma membrane.
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PMID:Spontaneous and detergent-induced vesiculation of thymocyte plasma membranes. 624 81

A phosphodiesterase activity is shown to copurify with the plasma membrane fraction prepared by the two-phase partition method. The enrichment in phosphodiesterase parallels that of alkaline phosphatase, which is thought to be a typical membranous enzyme. Up to 66% of the phosphodiesterase activity can be solubilized by a treatment with 0.2% Triton X-100. Higher doses were ineffective in solubilizing more activity. Analysis by native gel electrophoresis showed that an activity extracted by 2 M NaCl migrated at the same position as 'soluble' phosphodiesterase of cytosolic or extracellular origin. In contrast, the Triton-solubilized enzyme had an apparently higher molecular weight. When subjected to charge shift electrophoresis on agarose gels in the presence of an ionic detergent, the Triton-solubilized phosphodiesterase displayed a hydrophobic character. This behaviour contrasts with that of 'soluble' phosphodiesterases, the electrophoretic mobility of which is unaffected by the presence of an anionic detergent. The hydrophobic character of the membranous enzyme was lost after gentle hydrolysis by papain.
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PMID:The hydrophobic character of the membrane-bound phosphodiesterase from Dictyostelium discoideum. 626 Feb 58

The intracellular distribution of phosphodiesterase [EC 3.1.4.17] induced by cyclic adenosine 3',5'-monophosphate (cAMP) in Dictyostelium discoideum was studied. When cAMP-treated cells were homogenized and fractionated according to the method of de Duve et al. ((1955) Biochem, J. 60, 604), the specific activity of phosphodiesterase was highest in the light mitochondrial fraction. Peaks of specific activities of alkaline phosphatase (marker enzyme of membrane) and catalase (marker enzyme of peroxisomes) also appeared in the same fraction as phosphodiesterase. However, after centrifugation of the light mitochondrial fraction in a sucrose density gradient, the activity of phosphodiesterase was clearly separated with that of catalase (density 1.19 g/ml) and showed three peaks at lower density (1.10, 1.13, 1.17 g/ml) with good reproducibility. Some parts (1.13, 1.17 g/ml) of the activity in the gradient overlapped with alkaline phosphatase activity, but in the density fraction of 1.10 g/ml the activity of alkaline phosphatase was hardly detectable. When the light mitochondrial fraction was treated with Emulgen 108, or sonicated, phosphodiesterase was more easily solubilized than alkaline phosphatase and catalase, and was found in supernate after centrifugation at 20,000 X g for 30 min. In order to distinguish the locations of the three enzymes, the supernatant of the light mitochondrial fraction treated with Emulgen 108 was subjected to charge shift electrophoresis. The electrophoretic mobilities of phosphodiesterase and catalase were unaffected by ionic detergent. However, alkaline phosphatase shifted towards the anode in the presence of anionic detergent (sodium deoxycholate), and shifted towards the cathode in cationic detergent (cetyltrimethylammonium bromide), relative to nonionic detergent (Emulgen 108) alone. Thus, some part of the phosphodiesterase induced by cAMP may be associated with the plasma membrane, but the remainder is localized in some kind of intracellular particle of lower density. Moreover, the association with the membrane or particle is more easily dissociated than that of alkaline phosphatase, and the liberated phosphodiesterase is rather hydrophilic.
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PMID:Intracellular localization of phosphodiesterase induced by cyclic adenosine 3',5'-monophosphate in Dictyostelium discoideum. 626 72

The isolated, brush-border membrane of Hymenolepis diminuta contained an enzyme which hydrolyzed phosphodiester bonds. This enzyme appeared to be a Type I phosphodiesterase (E. C. 3.1.4.1) (produces nucleoside 5'-phosphates) and had no activity against synthetic, Type II phosphodiesterase substrates (mononucleotides substituted at the 3' position). The effects of various potential inhibitors of enzymatic activity, and cation requirements of this enzyme, demonstrated a distinct difference between the phosphodiesterase and alkaline phosphatase activities of the isolated, brush-border membrane. SDS-polyacrylamide gel electrophoresis of the isolated membrane preparation, followed by localization of phosphodiesterase activity in the gels, indicated the enzyme had a molecular weight of approximately 87,000. Thus, the phosphodiesterase activity represents a previously undescribed, membrane-bound enzyme of the brush-border of Hymenolepis diminuta.
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PMID:Type I phosphodiesterase in the isolated, brush-border membrane of Hymenolepis diminuta. 627 42

Guinea pig epidermal DNAase I was purified from an epidermal extract by a procedure including DEAE-cellulose chromatography, Sephadex G-100 gel filtration and Con A-Sepharose affinity chromatography. The purified enzyme contained no detectable activities of acid DNAase, alkaline RNAase, phosphodiesterase or acid or alkaline phosphatase, but was contaminated with acid RNAase activity. The molecular weight of the enzyme was estimated to be 33 000 by sucrose density gradient centrifugation and Sephadex G-100 gel filtration. Its isoelectric point is 5.2 +/- 0.1. The enzyme requires divalent cations and exhibits two pH optima that are dependent on divalent cations: in the presence of Mn2+, the optimum pH is about 7.5 in 50 mM Tris-HCl buffer and in the presence of Mn2+, the pH is 6.4 in 50 mM cacodylate-HCl buffer. The enzyme hydrolyzes native DNA about 6-times faster than denatured DNA, producing 5'-phosphoryl and 3'-hydroxyl terminated oligonucleotides with an average chain length of about eight nucleotides, and converts double-stranded and circular DNA to relaxed and linear forms. The enzyme is inhibited by G-actin and antiserum against bovine pancreatic DNAase A. Thus this enzyme is classified as DNAase I.
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PMID:Purification and properties of a neutral endodeoxyribonuclease from guinea pig epidermis. 627 8


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