Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0027960 (mole)
 21,279 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The photoinduced reaction of phenylalanyl-tRNA synthetase (E.C.6.1.1.20) from E.coli MRE-600 with tRNAphe containing photoreative p-N3-C6H4-NHCOCH2-group attached to 4-thiouridine sU8 (azido-tRNAphe) was investigated. The attachment of this group does not influence the dissociation constant of the complex of Phe-tRNAphe with the enzyme, however it results in sevenfold increase of Km in the enzymatic aminoacylation of tRNAphe. Under irradiation at 300 nm at pH 5.8 the covalent binding of [14C]-Phe-azido-tRNAphe to the enzyme takes place 0.3 moles of the reagent being attached per mole of the enzyme. tRNA prevents the reaction. Phenylalanine, ATP,ADP,AMP, adenosine and pyrophosphate (2.5 xx 10(-3) M) don't affect neither the stability of the tRNA-enzyme complex nor the rate of the affinity labelling. The presence of the mixture of either phenylalanine or phenylalaninol with ATP as well as phenylalaninol adenylate exhibits 50% inhibition of the photoinduced reaction. Therefore, the reaction of [14C]-Phe-azido-tRNA with the enzyme is significantly less sensitive to the presence of the ligands than the reaction of chlorambucilyl-tRNA with the reactive group attached to the acceptor end of the tRNA studied in 1. It has been concluded that the kinetics of the affinity labelling does permit to discriminate the influence of the low molecular weight ligands of the enzyme on the different sites of the tRNA enzyme interaction.
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PMID:Affinity labelling of phenylalanyl-tRNA synthetase from E. coli MRE-600 by E. coli tRNAphe containing photoreactive group. 0 72

The dihydrofolate synthetase (EC 6.3.2.12) responsible for catalyzing the synthesis of dihydrofolic acid from dihydropteroic acid and L-glutamic acid was purified about 130-fold from extracts of Serratia indica IFO 3759 by ammonium sulfate fractionation, DEAE-Sephadex column chromatography, Sephadex G-200 gel filtration, and DEAE-cellulose column chromatography. The enzyme preparation obtained was shown to be homogeneous by DEAE-cellulose column chromatography and ultracentrifugal analysis. The sedimentation coefficient of this enzyme was 3.9 S, and the molecular weight was determined to be about 47,000 by Sephadex G-100. The optimum pH for the reaction was 9.0. The enzymatic reaction required dihydropteroate, L-glutamate and ATP as substrates, and Mg2+ and K+ as cofactors. gamma-L-Glutamyl-L-glutamic acid cannot replace L-glutamic acid as the substrate. Neither pteroic acid nor tetrahydropteroic acid can be used as the substrate. ATP was partially replaced by ITP or GTP. The enzyme reaction was inhibited by the addition of AD, but not by AMP. One mole of dihydrofolate, 1 mole of ADP and 1 mole of orthophosphate were produced from each 1 mole of dihydropteroic acid, L-glutamic acid, and ATP by the following equation: 7,8-Dihydropteroic acid ml-Glutamic acid matp Mg2+, K+ leads to Dihydrofolic acid + ADP + Pi. These results suggest that the systematic name for the dihydrofolate synthetase is 7,8-dihydropteroate: L-glutamate ligase (ADP).
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PMID:Purification and properties of the dihydrofolate synthetase from Serratia indica. 0 96

1. Histamine secretion from rat peritoneal mast cells occurs spontaneously in the absence of an external stimulus. Spontaneous secretion increases as the concentration of Sr in the extracellular medium is raised from 1 to 10 m-mole/l. Ca 0.1-10 m-mole/l. does not increase spontaneous secretion.2. Spontaneous histamine secretion in the presence of Sr occurs slowly compared with evoked histamine secretion, reaching a maximum only after more than 120 min incubation with Sr 10 m-mole/l. at 37 degrees C and pH 7.6. Phosphatidyl serine, 10 mug/ml., increases the rate of spontaneous secretion in the presence of Sr.3. The spontaneous secretion occurring in the presence of Sr is highly dependent on the extracellular H ion concentration. Maximal secretion occurs at pH 8.4 and only a very limited secretion is detected at pH below 7.6. The rate of spontaneous secretion is also greater at higher pH. Inhibition of secretion caused by lowering the pH can be reversed by raising the Sr ion concentration over a limited range.4. Intact glycolytic and oxidative metabolism is required for the spontaneous secretion of histamine in the presence of Sr. Removal of extracellular glucose inhibits the secretion by about 80%, and the further addition of inhibitors of oxidative phosphorylation almost abolishes the secretion.5. Ca, Mg and Mn all inhibit the spontaneous secretion of histamine which occurs in the presence of Sr. The antagonism of the effect of Sr by Mg appears not to be competitive.6. Dibutyryl cyclic AMP, 10 mumole/l. to 3 m-mole/l. and theophylline, 30 mumole/l. inhibit spontaneous secretion in the presence of Sr. Cyclic AMP, AMP, and cyclic GMP 10 m-mole/l. are without effect on the spontaneous secretion. The inhibitory effect of dibutyryl cyclic AMP and of theophylline are dependent on pH: greater inhibition being achieved at lower pH.
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PMID:Spontaneous histamine secretion from mast cells in the presence of strontium. 7 47

1. Non-stimulated mast cells take up (89)Sr and (45)Ca. There is a rapid phase of uptake of both labels which is complete in 1 min and the (89)Sr uptake is similar in magnitude to the (45)Ca uptake. A further slower phase of uptake occurs in the period from 1 to 30 min of incubation. The magnitude of this slower phase is about 6 times greater for (89)Sr than for (45)Ca.2. Non-stimulated and antigen-stimulated mast cells accumulate Sr which can be measured by atomic absorption spectroscopy. There is a direct relationship between Sr accumulation and histamine secretion which is independent of whether or not the cells are stimulated. 10% histamine secretion is associated with Sr accumulation of 0.25 f-mole/cell.3. The time course of (89)Sr uptake is similar to the time course of histamine secretion in non-stimulated cells.4. The uptake of (89)Sr is linearly related to the external Sr concentration in the range 0.5-16 m-mole/l. for both stimulated and non-stimulated cells.5. Ca, 10-1000 mumole/l. inhibits (89)Sr uptake in non-stimulated cells.6. Inhibition of glycolysis and oxidative phosphorylation prevents spontaneous histamine secretion in the presence of Sr without blocking the accumulation of Sr by the cells.7. Dibutyryl cyclic AMP, 10 m-mole/l. produces only 18% inhibition of (89)Sr uptake whereas histamine secretion is inhibited by 45% by the same concentration. The antigen-stimulated Sr uptake on the other hand can be completely inhibited by dibutyryl cyclic AMP, 10 m-mole/l.8. The uptakes of (89)Sr and Sr by unstimulated mast cells after 60 min incubation are dependent on extracellular H ion concentration. Both uptakes increase with increasing pH over the range pH 7-8.5.
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PMID:Movement of strontium ions into mast cells and its relationship to the secretory response. 7 48

Mitochondrial ATPase from rat liver mitochondria contains multiple nucleotide binding sites. At low concentrations ADP binds with high affinity (1 mole/mole ATPase, KD = 1-2 muM). At high concentrations, ADP inhibits ATP hydrolysis presumably by competing with ATP for the active site (KI = 240-300 muM). As isolated, mitochondrial ATPase contains between 0.6 and 2.5 moles ATP/mole ATPase. This "tightly bound" ATP can be removed by repeated precipitations with ammonium sulfate without altering hydrolytic activity of the enzyme. However, the ATP-depleted enzyme must be redissolved in high concentrations of phosphate to retain activity. AMP-PNP (adenylyl imidodiphosphate) replaces tightly bound ATP removed from the enzyme and inhibits ATP hydrolysis. AMP-PNP has little effect on high affinity binding of ADP. Kinetics studies of ATP hydrolysis reveal hyperbolic velocity vs. ATP plots, provided assays are done in bicarbonate buffer or buffers containing high concentrations of phosphate. Taken together, these studies indicate that sites on the enzyme not directly associated with ATP hydrolysis bind ATP or ADP, and that in the absence of bound nucleotide, Pi can maintain the active form of the enzyme.
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PMID:Interaction of homogeneous mitochondrial ATPase from rat liver with adenine nucleotides and inorganic phosphate. 12 85

Accelerated calcium transport into the sarcoplasmic reticulum (SR) of the heart may mediate the inotropic actions of agents that act to increase adenosine 3',5'-monophosphate (cyclic AMP) within the cell. Studies in our laboratory have shown that ATP-dependent Ca uptake by cardiac microsomes rich in SR is enhanced by pretreatment with bovine cardiac cyclic AMP-dependent protein kinase (cyclic AMP-PK). Ca2+-activated ATPase is increased concomitantly with Ca uptake, stoichiometric coupling of 2 moles of Ca2+ taken up per mole of ATP hydrolyzed remaining constant. The steady state level of Ca binding is not increased by cyclic AMP-PK pretreatment, suggesting that the turnover rate of the transport system rather than the number of transport sites is increased. Phosphorylation of the SR by protein kinase is half-maximal at approximately 10(-7) M cyclic AMP, a value similar to that which gives half-maximal stimulation of both Ca uptake and Ca2+-activated ATPase. Over 80 percent of the 32P associated with membrane protein is identifiable as phosphoserine and phosphothreonine. The 32P is incorporated into a 22,000-dalton protein as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This protein, which we have tentatively named phospholamban (lambda alpha mu beta alpha psi usilon epsilon omega = to receive) appears to particiapte in the regulation of calcium transport by the heart's SR and may play a role in the inotropic actions of drugs, such as epinephrine, which act upon the cyclic AMP-PK system.
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PMID:Phospholamban: a regulatory protein of the cardiac sarcoplasmic reticulum. 12 51

Tightly bound adenine nucleotides are removed from multiple binding sites on beef heart mitochondrial ATPase (F1) by chromatography on columns of Sephadex equilibrated with 50% glycerol. Release of nucleotides from the enzyme is associated with large decreases in sedimentation velocity (from 11.9 S to 8.4 S) which may be observed in concentrated solutions of polyols. Polyol-induced conformational changes are reversed when the enzyme is returned to dilute buffers. The nucleotide-depleted enzyme restores oxidative phosphorylation in F1-deficient submitochondrial particles. Reconstitution of nucleotide-depleted F1 with the ATP analog (adenylyl-imidodiphosphate (AMP-PNP), almost 5 moles of AMP-PNP per mole of enzyme, results in preparations with substantially inhibited ATPase activity which nevertheless restores oxidative phosphorylation and the 32Pi-ATP exchange reaction in F1-deficient submitochondrial particles. Incubation of the analog-labeled enzyme with ATP and Mg++ results in partial displacement of the analog and a time-dependent recovery of ATPase activity.
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PMID:Physical and enzymatic properties of nucleotide-depleted beef heart mitochondrial adenosine triphosphatase. 12 61

Microtubules prepared from chick brain homogenates by successive cycles of assembly-disassembly were found to contain two high-molecular-weight proteins, designated microtubule-associated protein1 and microtubule-associated protein2. Microtubule-associated protein2 (apparent molecular weight 300,000 by sodium dodecyl sulfate-polyacrylamide gel electrophoresis) was the preferred substrate for an endogenous cyclic AMP-dependent protein kinase which appeared to be an integral component of the microtubules. The initial rate of phosphorylation of microtubule-associated protein2 was enhanced 4- to 6-fold by cyclic AMP, with half-maximal stimulation occurring at 2 times 10-7 M cyclic AMP. Under optimal conditions, a total of 1.0 and 1.9 mol of phosphate was incorporated per mole of microtubule-associated protein2, in the absence and presence of cyclic AMP, respectively. Cyclic AMP also stimulated the phosphorylation of tubulin, but the rate of phosphate incorporation per mol of tubulin was only 0.15% that of microtubule-associated protein2. The data raise the possibility that the cyclic AMP-dependent phosphorylation of microtubule-associated protein 2 may play a role in microtubule assembly or function.
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PMID:Cyclic AMP-dependent endogenous phosphorylation of a microtubule-associated protein. 16 13

Modification of pig kidney fructose 1,6-bisphosphatase with 2,3-butanedione (in the presence of AMP) results in the loss of activation of the enzyme by monovalent cations. Under these conditions about 8 arginyl residues per mole of enzyme were modified. No other residues were modified. No loss of monovalent cation activation occurs when modification with 2,3-butanedione is carried out in the presence of AMP plus the substrate fructose 1,6-bisphosphate and 3.2 less arginyl residues were modified. Since fructose 1,6-bisphosphatase contains 4 subunits, it is suggested that one arginyl residue per subunit plays an essential role in monovalent cation activation of the enzyme. Studies on sulfhydryl group reactivity toward 5,5'-dithiobis(2-nitrobenzoic acid) explain the protection exerted by fructose 1,6-bisphosphate against the loss of monovalent cation activation in terms of an enzyme conformational change induced by substrate, which makes unreactive the essential arginyl residue. The results of the present paper, as well as previous evidence, are discussed in terms of the mechanism of monovalent cation activation of fructose 1,6-biphosphatase.
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PMID:Functional consequences of modifying highly reactive arginyl residues of fructose 1,6-bisphosphatase. Loss of monovalent cation activation. 16 92

A glucagon-saline solution (0.1 ml, 10(7) mole/100 g body weight) was injected via the portal vein into nonfasted Wistar and carbohydrate-sensitive BHE rats. Levels of liver and epididymal fat pad cyclic-AMP were observed after 6 and 24 minutes. When compared to sham injected rats at 6 minutes, glucagon injected rats of both strains had twice the level of cyclie-AMP in liver and fat pad tissue. By 24 minutes, the cyclic-AMP levels of the Wistar rats had decreased to those observed in their sham injected counterparts, and the concentration of liver cyclic-AMP in both sham injected and glucagon injected BHE rats had decreased to levels significantly below those observed in the Wistar rats. This observation suggests that a lipolytic-lipogenic imbalance may reside in the livers of rats of the BHE strain.
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PMID:Rat strain differences in cyclic-AMP levels in liver and epididymal fat pad tissue as influenced by glucagon. 18 45


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