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:3.5.1.4 (deaminase)
5,113 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

AMP deaminase (AMP aminohydrolase, EC 3.5.4.6) was found in extract of baker's yeast (Saccharomyces cerevisiae), and was purified to electrophoretic homogeneity using phosphocellulose adsorption chromatography and affinity elution by ATP. The enzyme shows cooperative binding of AMP (Hill coefficient, nH, 1.7) with an s0.5 value of 2.6 mM in the absence or presence of alkali metals. ATP acts as a positive effector, lowering nH to 1.0 and s0.5 to 0.02 mM. P1 inhibits the enzyme in an allosteric manner: s0.5 and nH values increase with increase in Pi concentration. In the physiological range of adenylate energy charge in yeast cells (0.5 to 0.9), the AMP deaminase activity increases sharply with decreasing energy charge, and the decrease in the size of adenylate pool causes a marked decrease in the rate of the deaminase reaction. AMP deaminase may act as a part of the system that protects against wide excursions of energy charge and adenylate pool size in yeast cells. These suggestions, based on the properties of the enzyme observed in vitro, are consistent with the results of experiments on baker's yeast in vivo reported by other workers.
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PMID:AMP deaminase from baker's yeast. Purification and some regulatory properties. 3 10

1. Kinetic data for avian erythrocyte AMP-deaminase in lysate supernatants and 2000-fold purified enzyme were consistent with an allosteric model having four binding sites for substrate. 2. Relative to the purified enzyme, AMP-deaminase in lysate supernatants exhibited a greater S0.5 and enhanced sensitivity toward phytic acid, but was far less sensitive toward potassium ion. 3. In the absence of potassium chloride, the enzymatic activity in lysates exhibited hysteresis at subsaturating 5'-AMP. This response was modified reversibly by allosteric ligands. 4. It is concluded that the characteristics of avian RBC AMP-deaminase, as expressed in lysates, may reflect important intermolecular interactions and better represent the regulatory properties of this enzyme in erythrocytes.
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PMID:Regulation of avian erythrocyte AMP-deaminase. 4 52

Adenosine and the adenine nucleotides have a potent depressant action on cerebral cortical neurons, including identified corticospinal cells. Other purine and pyrimidine nucleotides were either weakly depressant (inosine and guanosine derivatives) or largely inactive (xanthine, cytidine, thymidine, uridine derivatives). The 5'-triphosphates and to a lesser extent the 5'-diphosphates of all the purine and pyrimidines tested had excitant actions on cortical neurons. Adenosine transport blockers and deaminase inhibitors depressed the firing of cortical neurons and potentiated the depressant actions of adenosine and the adenine nucleotides. Methylxanthines (theophylline, caffeine, and isobutylmethylxanthine) antagonized the depressant effects of adenosine and the adenine nucleotides and enhanced the spontaneous firing rate of cerebral cortical neurons. Intracellular recordings showed that adenosine 5'-monophosphate hyperpolarizes cerebral cortical neurons and suppresses spontaneous and evoked excitatory postsynaptic potentials in the absence of any pronounced alterations in membrane resistance or of the threshold for action potential generation. It is suggested that adenosine depresses spontaneous and evoked activity by inhibiting the release of transmitter from presynaptic nerve terminals. Furthermore, the depressant effects of potentiators and excitant effects of antagonists of adenosine on neuronal firing are consistent with the hypothesis that cortical neurons are subject to control by endogenously released purines.
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PMID:Effects of adenosine and adenine nucleotides on synaptic transmission in the cerebral cortex. 9 18

The specific activities of enzymes participating in AMP-catabolizing reactions in promastigotes of Leishmania tropica were determined. The following sequence of reactions is suggested: AMP leads to adenosine leads to adenine leads to hypoxanthine. The initial enzyme of this sequence, AMP nucleotidase, is apparently membrane-bound. The significance of AMP catabolism with respect to adenylate energy charge and a signal transfering mechanism is discussed. Adenine deaminase has been partially purified and characterized. Several purine analogues, inter alia allopurinol, proved to be inhibitors of the adenine deaminase catalyzed reaction.
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PMID:Catabolism of adenosine 5'-monophosphate in promastigotes of Leishmania tropica. 10 64

Concentrations of key metabolites were determined in carp white muscle before exercise and after maximal activity. It was found that the concentration of ATP decreases by about 65%, ADP decreases slightly, and AMP remains unchanged. Consequently, the level of the free adenylate pool decreases. Simultaneously there is an increase in the concentration of IMP and NH4+. The increase in IMP level and the decrease in adenylate pool are essentially in 1:1 stoichiometry, a result showing that the adenylate pool is decreased by the reaction catalyzed by 5'-AMP deaminase (EC 3.5.4.6.). During exercise there is an increase in levels of glucose-6-phosphate, fructose 6-phosphate, and fructose 1,6-diphosphate that, along with the decrease in ATP levels, can account for the increase in glycolytic flux by activation of phosphofructokinase and pyruvate kinase.
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PMID:Control of energy metabolism in fish white muscle. 13 93

The regulatory properties of adenylate deaminase (EC 3.5.4.6) from Ehrlich ascites tumor cells suggest that the reaction catalyzed by this enzyme serves to protect the cell against sharp decreases in the adenylate energy charge by removing adenosine 5'-monophosphate generated when the rate of utilization of adenosine triphosphate is suddenly increased. The enzyme is effectively inhibited under normal physiological conditions of high energy charge (0.9) and 4 to 5 mM adenine nucleotide pool size. The reaction is sharply activated by a decrease in the energy charge in the physiological range (0.9 to 0.6). At low energy charge (0.6), decrease in the size of the pool causes a marked and nonlinear decrease in the rate of the deaminase reaction. This effect presumably serves to prevent excessive depletion of the adenine nucleotide pool. Calculations based on the kinetic data obtained in this study show that the AMP deaminase reaction can account for the well-established alteration of adenine nucleotide metabolism that is observed following addition of glucose or 2-deoxyglucose to intact ascites cells.
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PMID:Role of the adenylate deaminase reaction in regulation of adenine nucleotide metabolism in Ehrlich ascites tumor cells. 94 36

Angiotensin II has been found to stimulate 5'-adenylic acid deaminase from rabbit skeletal muscle. Stimulation was discernible around 10(-9) M and peak stimulation of about threefold was seen at 10(-7) M, concentrations approximating those required for stimulation of vascular smooth muscle or adrenal glomerulosa cells. Higher concentrations produced less stimulation. Adenosine triphosphate stimulated to the same degree, but a concentration of 10(-5) M was required for maximum stimulation, while maximum stimulation with sodium or potassium required 0.5 M and 0.75 M, respectively. Although the physiologic significance of these observations has not been established, these data suggest an intracellular role for angiotensin II.
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PMID:Angiotensin II stimulation of 5'-adenylic acid deaminase. 125 Aug 47

ADP-ribose was detected in human red blood cells (RBC) at 0.45 +/- 0.1 microM concentrations. These levels could be estimated after purification of ADP-ribose by means of three sequential HPLC fractionations of RBC extracts. Extraction was performed by sonication of RBC either in trichloroacetic acid, followed by centrifugation, or in carbonate-bicarbonate buffer, pH 10.0, followed by rapid ultrafiltration. Neither procedure of extraction caused artefactual formation of ADP-ribose. Prolonged incubation of intact RBC in isotonic buffer containing labeled orthophosphate resulted in the slow incorporation of radioactivity into ADP-ribose. Identification of the labeled ADP-ribose was confirmed upon incubation of the purified metabolite with nucleotide pyrophosphatase, yielding radioactive 5'-AMP and ribose 5-phosphate, while its exposure to a nonspecific deaminase resulted in the quantitative formation of labeled inosine diphosphate ribose.
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PMID:Presence and turnover of adenosine diphosphate ribose in human erythrocytes. 141 62

AMP-deaminase from human kidney (cortex and medulla) was purified and the physicochemical properties were characterized. The enzyme from both portions of the kidney exhibited identical kinetics and regulatory properties. At optimal pH (6.6), the AMP-deaminase studied exhibited a distinctly sigmoidal substrate saturation kinetics, with the half-saturation parameter (S0.5) as high as 10 mM. ATP at 1 mM strongly activated the enzyme, decreasing S0.5 nearly 10-fold. The activating effect of ADP was less strong. Orthophosphate inhibited the enzyme, but the inhibition observed was weak (Ki approximately 16 mM) and had a pure competitive character. At pH 7.2, physiological for the kidney cortex, orthophosphate inhibition became even weaker and became partially competitive. Variations in the adenylate energy charge had potent effects on the activity of AMP-deaminase, depending on the size of the total adenine nucleotide pool examined. The results of gel filtration and SDS-PAGE indicated that human kidney AMP-deaminase is an oligomeric enzyme composed of four, probably identical, subunits weighing about 37 kDa each.
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PMID:Purification and properties of AMP-deaminase from human kidney. 162 54

At pH 7.0 and physiological concentrations of the main regulatory ligands (ATP, ADP, orthophosphate), human uterine muscle AMP-deaminase follows a hyperbolic type of saturation kinetics with S0.5 parameter value about 2 mM. The enzyme is regulated by adenylate energy charge (AEC) variations, being the most active at the AEC value 0.5-0.6 or 0.5-0.7, depending on the size of the total adenine nucleotide pool. Long-chain acyl-CoA strongly inhibit activity of the enzyme, influencing mainly the maximum velocity of the reaction.
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PMID:Purification and properties of AMP-deaminase from human uterine smooth muscle. Regulation by adenylate energy charge and activated fatty acids. 206 99


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