Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts:   Target Concepts:
Query: EC:3.1.4.1 (phosphodiesterase)
 18,767 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A procedure for the quantitative measurement of the O2'-methylnucleoside constitutents of RNA has recently been developed in this laboratory (Gray, M.W. Can. J. Biochem. 53, 735-746 (1975)). This assay method is based on the resistance of O2'-methylnucleoside 5'-phosphates (pNm) (generated by phosphodiesterase hydrolysis of RNA) to subsequent dephosphorylation by venom 5'-nucleotidase (EC 3.1.3.5). In the present investigation, two base-modified 5'-nucleotides, each displaying an unusual resistance to 5'-nucleotidase, have been identified. These compounds have been characterized by a variety of techniques as N2, N2-dimethylguanosine 5'-phosphate (pm2/2G) and 3-(3-amino-3-carboxypropyl)uridine 5'-phosphate (p4abu3U). Because of their resistance to 5'-nucleotidase, pm2/2G and p4abu3U are isolated along with the pNm in the mononucleotide fraction of venom hydrolysates of transfer RNA. Under hydrolysis conditions, the stability of p4abu3U is comparable to that of a pNm, allowing quantitative assay of the nucleotide. The proportion (mean +/- SD) of p4abu3U in venom hydrolysates of wheat embryo and Escherichia coli tRNA has been determined to be 0.35 +/- 0.03 (n=5) and 0.14 +/- 0.02 (n=4) mol%, respectively. The absence of p4abu3U in venom hydrolysates of yeast tRNA implies the absence of the corresponding nucleoside in yeast tRNA, in agreement with existing data. The variable recovery of pm2/2G from venom hydrolysates of wheat embryo and yeast tRNA indicates that under hydrolysis conditions, this base-modified nucleotide is only partially resistent to 5'-nucleotidase. The complete absence of pm2/2G in venom hydrolysates of E. coli tRNA is consistent with the known absence of N2, N2-dimethylguanosine in this RNA. These observations demonstrate that resistance to 5'-nucleotidase is a necessary but not sufficient criterion for concluding that a 5'-nucleotide is O2'-methylated. When applied to wheat embryo ribosomal RNA, the analytical methods described in this report failed to reveal any compound having the distinctive charge properties of p4abu3U. It therefore appears that 1-methyl-3-(3-amino-3-carboxypropyl)pseudouridine, recently characterized as a constituent of the 18 S rRNA of Chinese hamster cells (Saponara, A.G. & Enger, M.D. Biochim. Biophys. Acta 349, 61-77 (1974)), may not be present in wheat embryo ribosomal RNA.
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PMID:Modified 5'-nucleotides resistant to 5'-nucleotidase: isolation of 3-(3-amino-3-carboxypropyl) uridine 5'-phosphate and N2, N2-dimethylguanosine 5'-phosphate from snake venom hydrolysates of transfer RNA. 0 33

The activities of guanylate cyclase, guanosine 3', 5'-monophosphate (cyclic GMP) phosphodiesterase and 5'-nucleotidase were measured during postnatal development in retinas of control and C3H/HeJ mice. In control retina, each of these enzyme activities increases in conjunction with photoreceptor cell differentiation and maturation. In C3H retina, guanylate cyclase and 5-nucleotidase activities increase with photoreceptor cell development and decrease with photoreceptor cell death. However, the activity of a class of cyclic GMP phosphodiesterase which distinguishes the photoreceptor cells of control mice and those of several other species is not demonstrable in retina of C3H mice at any age. It is suggested that the deficiency in cyclic GMP phosphodiesterase activity may account for the accumulation of cyclic GMP which has been shown to occur in the C3H photoreceptor cells before they degenerate.
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PMID:Enzymic basis for cyclic GMP accumulation in degenerative photoreceptor cells of mouse retina. 0 93

1. Highly sensitive technique are described for the assay of plasma membrane (5'-nucleotidase, alkaline phosphatase), microsomal (neutral alpha-glucosidase, leucyl-2-naphthylamidase) and biliary canalicular (gamma-glutamyltransferase) enzymes and for nine acid hydrolases (acid phosphatase, phosphodiesterase, beta-glucosidase, alpha-glucosidase, alpha-galactosidase, beta-galactosidase, alpha-mannosidase, N-acetyl-beta-glucosaminidase, beta-glucuronidase) in human liver. 2. Optimum and specific assay systems have been developed which give linear kinetics for all enzymes. 3. The range of enzyme activities in samples of human liver, obtained by closed needle biopsy, and sera have been determined.
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PMID:Enzyme activities in human liver biopsies: assay methods and activities of some lysosomal and membrane-bound enzymes in control tissue and serum. 1 4

Large amounts (66-97%) of marker enzymes such as alkaline phosphatase, 5'-nucleotidase, phosphodiesterase I, and gamma-glutamyl transpeptidase of bovine milk fat globule membrane (MFGM) were selectively solubilized by nonionic detergents such as Triton X-100, Tween 20, Nonidet P-40, Liponox NCK, and Emulgen 109-P. On the other hand, the extractability of MFGM protein with these detergents was less than 50%. Judging from the recovery of total activity, it is likely that alkaline phosphatase, phosphodiesterase I, and gamma-glutamyl transpeptidase are activated by nonionic detergents, whereas 5'-nucleotidase is somewhat inhibited by the detergents, except for Tween 20, and acid phosphatase is strongly inhibited by all detergents. In addition, solubilization of the protein with the nonionic detergents was found to be somewhat selective by SDS-polyacrylamide gel electrophoresis. There was no appreciable difference between the five brands of nonionic detergents used as regards the extractability of protein and the enzymatic activity of the extracted marker enzymes of MFGM, except that the solubilizing ability of Tween 20 was relatively low.
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PMID:Selective extraction of marker enzymes of bovine milk fat globule membrane by nonionic detergents. 3 79

Two of the new anticancer drugs recently synthesized in our laboratory from conjugation of ara-C2 and several corticosteroids linked through a phosphodiester bond include prednisolone- (I) and prednisone-p-ara-C (II). They were demonstrated to be enzymatically hydrolyzed to the corresponding steroid and ara-CMP and the latter was further shown to be hydrolyzed to ara-C by phosphodiesterase I, snake venom, 5'-nucleotidase, and acid phosphatase. However, the conjugates were shown to be resistant to hydrolysis by alkaline phosphatase. The activity of conjugates I and II against L1210 lymphoid leukemia in female mice (C3D2F1/J) was significantly greater than that of ara-C alone or in combination with the steroid. In fact, when the optimum dosage of 75 (mumol/kg)/day x 5 was used, the administration of ara-C alone was followed by an increased life span (ILS) of 45%. This result is similar to that previously reported. With the same equimolar doses of mixtures of ara-C and either prednisolone or prednisone, the ILS values were 40 and 44%, respectively. However, when the conjugates were used, the ILS values were 89 and 100% respectively. These findings seem promising and have provided the bases for continued study of these new compounds.
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PMID:Nucleoside conjugates as potential antitumor agents. 2. Synthesis and biological activity of 1-(beta-D-arabinofuranosyl)cytosine conjugates of prednisolone and prednisone. 11 58

1. Six rat liver plasma-membrane subfractions of different density and morphological, enzymic and chemical properties were prepared from homogenates by a combination of differential, rate-zonal and density-gradient centrifugation. They consisted of three vesicular 'light' subfractions of density 1.12-1.13 and three 'heavy' subfractions of density 1.16-1.18 containing membrane strips and intercellular junctions. 2. All six subfractions contained a basal adenylate cyclase activity. One of the 'light' subfractions that showed the highest glucagon-stimulated adenylate cyclase activity was identified as deriving form the blood-sinusoidal face of the hepatocyte. This subfraction, unlike the others, was contaminated by Golgi components, as indicated by its morphological properties and the presence of galactosyl- and sialyl-transferase activities. 3. All the six subfractions showed high activities of the following plasma-membrane marker enzymes: 5'-nucleotidase, alkaline phosphodiesterase (nucleotide pyrophosphatase), alkaline phosphatase, leucine naphthylamidase and Mg2+-activated adenosine triphosphatase. A 'light' subfraction that showed the highest specific activities of all the above marker enzymes, but lacked a glucagon-stimulated adenylate cyclase activity, was identified as deriving from the bile-canalicular face of the hepatocyte. 4. The 'heavy' subfractions, which showed generally the lowest activities of the above plasma-membrane enzyme markers, and were characterized by the presence of desmosomes and gap junctions, were taken to originate from the contiguous faces of the hepatocyte. 5. The protein composition of the six subfractions was generally similar, as shown by polyacrylamide-gel electrophoresis. Differences in the amounts of various protein and glycoprotein bands among the subfractions correlated with their morphology, enzymic composition and sialic acid content. 6. Hormonal and histochemical evidence supporting the identification of a bile-canalicular subfraction, a blood-sinusoidal subfraction and contiguous-face subfractions is discussed.
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PMID:Functional polarity of the rat hepatocyte surface membrane. Isolation and characterization of plasma-membrane subfractions from the blood-sinusoidal, bile-Canalicular and contiguous surfaces of the hepatocyte. 12 84

The concentration of cyclic AMP (cAMP) and its metabolites (5'-AMP and adenosine) as well as the adenyl cyclase, cAMP phosphodiesterase, and 5'-nucleotidase activities were determined in lymphocytes of thymus, spleen, and lymph nodes of control and protein-deficient rats. The values of these parameters, when expressed as per milligran DNA and as per 10-8 cells, but not always when expressed as per milligran protein, were much lower in the thymus as compared with the spleen and the lymph nodes in the control rats. The protein-deficient diet increased the nucleotide concentrations in the thymus and spleen lymphocytes on a per milligram DNA basis except those of thymic cAMP, which did not change. The same diet also increased the activities of the enzymes involved in the cAMP metabolism in thymic, splenic, and lymph node lymphocytes. Such a peculiarity could be related to the reduction of the mitotic activity of lymphocytes caused by protein deficiency since an inverse relationship has been reported between this activity and the synthesis of cAMP. On the other hand, it was noted that purified lymphocyte suspensions contained paradoxically higher amounts per cell of DNA, RNA, and protein in the thymus, spleen, and lymph nodes of protein-deficient rats as compared with those of the control rats. However, when the cell preparations were not purified, only the lymph node cells displayed a strong increase in their DNA content. Prolongation of the S phase of the cell cycle in these lymphocytes is suggested.
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PMID:Cyclic AMP metabolism and nucleic acid content in the lymphocytes of the thymus, spleen, and lymph nodes of protein-deficient rats. 16 50

We have perfused isolated rat livers with hypocalcemic (4.4 mg 100 ml) Krebs-Ringer bicarbonate albumin buffer. After 15 min of perfusion, a substance appeared in the perfusate which decreased rat renal adenylate cyclase activation by parathyroid hormone (PTH). The material in the perfusate was purified greater than 50,000-fold by Bio-Gel P-10 chromatography. The purified antagonist decreased the activation of rat renal cortical adenylate cyclase by PTH, glucagon, and epinephrine 75 to 100%. Concentration response curves for each of the hormones indicated a noncompetitive interaction of the inhibitor with the hormone. The inhibition was not species-specific, as the activation of the parathyroid hormone-responsive adenylate cyclase in cat renal cortex was also abolished by the inhibitor from the perfused rat liver. The inhibitor is a peptide, Mr equal to similar to 1000, which is heat-stable, acid-stable, alkai-labile, and is destroyed by trypsin, leucine aminopeptidase, and elastase. It is not destroyed by phosphodiesterase, 5'-nucleotidase, alkaline phosphatase, neuraminidase, RNase, or phospholipase A. The inhibitor is not produced by isolated rat livers perfused with normocalcemic perfusion media. It is unclear whether the peptide is synthesized by the liver or whether it is a breakdown product of a larger peptide or protein in the liver. This is the first reported peptide inhibitor of adenylate cyclase.
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PMID:Isolation of a unique peptide inhibitor of hormone-responsive adenylate cyclase. 16 24

Plasma membranes from 6 spontaneously metastasizing and 4 non-metastasizing rat mammary carcinomata were isolated by discontinuous sucrose density gradient centrifugation of microsomal pellets. The starting microsomal fraction contained 40-50% plasma membranes as determined by the levels of 5'-nucleotidase activity, with a negligible amount of nuclear (1%), mitochondrial (5%) and lysomal (7%) contamination. Five distinct fractions (F1-F5) were banded at densities 1 X 09, 1 X 13, 1 X 15, 1 X 17 and 1 X 21 at 25 degrees C, in addition to a pellet (F6) obtained by centrifuging at 76,000 g for 17 h. The fractions F1 through F5, all contained various concentrations of membranous structures, while the pellet (F6) contained only amorphous materials as evidenced by electron microscopy. The F3 fraction at the gradient 1 X 15 had the highest specific as well as total activity of the plasma membrane marker enzyme, with aggregates of the least contaminated plasma membranes in vesicular forms. This fraction also had the lowest specific activity for glucose-6-phosphatase (smooth ER marker) and for beta-D-glucuronidase (lysomal marker), and therefore was considered to be the "cleanest" plasma membrane fraction. When the activity of 4 additional plasma membrane marker enzymes, i.e., alkaline phosphatase, phosphodiesterase I, nucleotide pyrophosphatase and alkaline ribonuclease was determined in the same F3 fraction, their levels were significantly lower in every metastasizing tumour than in the non-metastasizing ones, with the enzyme activity decreasing in direct proportion to the metastasizing capacity. On the other hand, the marker enzymes were high in all non-metastasizing tumours, with the activity seemingly increasing with the immunogenicity of tumour cells. There was no significant difference between the 2 groups of mammary tumours in the levels of sialic acid, hexosamine, phospholipid or cholesterol in the plasma membranes. Thus, the level of plasma membrane marker enzymes is considered an accurate indicator for metastasizing capacity in the rat mammary tumour system.
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PMID:Plasma membrane associated enzymes of mammary tumours as the biochemical indicators of metastasizing capacity. Analyses of enriched plasma membrane preparations. 17 19

Subcellular fractions were obtained from aortas and ventricles of 6-month-old spontaneously hypertensive and normotensive Wistar rats by the use of differential and sucrose density gradient centrifugation. These preparations were studied to determine what alterations in calcium accumulation and enzymatic activities might be associated with hypertension. The total amount of calcium accumulation (in the presence of ATP and 17 muM free calcium) by the plasma membrane-enriched fraction from hypertensive rat aortas significantly less than that from normotensive rats (11.3 +/- 0.4 vs 16.2 +/- 1.6 mumol of calcium/g of protein, n = 8). In contrast the specific activities of the plasma membrane marker enzymes, 5'-nucleotidase and phosphodiesterase I, were 80% and 40% greater, respectively, in the hypertensive than in the normotensive fractions. On the other hand, various fractions from ventricles of the two types of rats were generally similar in enzyme activities and calcium accumulation. The decreased rate of relaxation of aortas from spontaneously hypertensive rats may be caused by the decreased rate of calcium transport demonstrated in this study.
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PMID:Calcium accumulation and enzymatic activities of subcellular fractions from aortas and ventricles of genetically hypertensive rats. 17 22


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