Effects of adenine nucleotides and phosphate on adenosine triphosphate sulphurylase from Anabaena cylindrica.
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ABSTRACT:
SUBMITTER: Sawhney SK
PROVIDER: S-EPMC1164770 | biostudies-other | 1977 Apr
REPOSITORIES: biostudies-other
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Project description:The presence of ATP sulphurylase activity in the 30000g supernatant fraction of rice-root homogenate has been demonstrated. Studies of the effects of adenosine and its nucleotides on the enzymic activity showed that AMP activated but that ADP and adenosine inhibited the enzyme.
| S-EPMC1165619 | biostudies-other
Project description:1. ATP sulphurylase from Saccharomyces cerevisiae was purified 140-fold by using heat treatment, DEAE-cellulose chromatography and Sepharose 6B gel filtration. 2. The enzyme was stable at -15 degrees C, optimum reaction velocity was between pH7.0 and 9.0, and the activation energy was 62kJ/mol (14.7kcal/mol). 3. The substrate was shown to be the MgATP(2-) complex, free ATP being inhibitory. 4. Double-reciprocal plots from initial-velocity studies were intersecting and the K(m) of each substrate was determined at infinite concentration of the other (K(m) MgATP(2-), 0.07mm; MoO(4) (2-), 0.17mm). 5. Radio-isotopic exchange between the substrate pairs, adenosine 5'-[(35)S]sulphatophosphate and SO(4) (2-), (35)SO(4) (2-) and adenosine 5'-sulphatophosphate, occurred only in the presence of either MgATP(2-) or PP(i). This suggests, along with the initial-velocity data, a sequential reaction mechanism in which both substrates bind before any product is released. 6. The enzyme reaction was specific for ATP and was not inhibited by l-cysteine, l-methionine, SO(3) (2-), S(2)O(3) (2-) (all 2mm) nor by p-chloromercuribenzoate (1mm). 7. Competitive inhibition of the enzyme with respect to MoO(4) (2-) was produced by SO(4) (2-) (K(i)=2.0mm) and non-competitive inhibition by sulphide (K(i)=3.4mm). 8. Adenosine 5'-sulphatophosphate inhibited strongly and concentrations as low as 0.02mm altered the normal hyperbolic velocity-substrate curves with both MgATP(2-) and MoO(4) (2-) to sigmoidal forms.
| S-EPMC1177733 | biostudies-other
Project description:RATIONALE:Decreased alkaline phosphatase activity after infant cardiac surgery is associated with increased post-operative cardiovascular support requirements. In adults undergoing coronary artery bypass grafting, alkaline phosphatase infusion may reduce inflammation. Mechanisms underlying these effects have not been explored but may include decreased conversion of extracellular adenine nucleotides to adenosine. OBJECTIVES:1) Evaluate the association between alkaline phosphatase activity and serum conversion of adenosine monophosphate to adenosine after infant cardiac surgery; 2) assess if inhibition/supplementation of serum alkaline phosphatase modulates this conversion. METHODS AND RESEARCH:Pre/post-bypass serum samples were obtained from 75 infants <4 months of age. Serum conversion of 13C5-adenosine monophosphate to 13C5-adenosine was assessed with/without selective inhibition of alkaline phosphatase and CD73. Low and high concentration 13C5-adenosine monophosphate (simulating normal/stress concentrations) were used. Effects of alkaline phosphatase supplementation on adenosine monophosphate clearance were also assessed. Changes in serum alkaline phosphatase activity were strongly correlated with changes in 13C5-adenosine production with or without CD73 inhibition (r = 0.83; p<0.0001). Serum with low alkaline phosphatase activity (?80 U/L) generated significantly less 13C5-adenosine, particularly in the presence of high concentration 13C5-adenosine monophosphate (10.4?mol/L vs 12.9?mol/L; p = 0.0004). Inhibition of alkaline phosphatase led to a marked decrease in 13C5-adenosine production (11.9?mol/L vs 2.7?mol/L; p<0.0001). Supplementation with physiologic dose human tissue non-specific alkaline phosphatase or high dose bovine intestinal alkaline phosphatase doubled 13C5-adenosine monophosphate conversion to 13C5-adenosine (p<0.0001). CONCLUSIONS:Alkaline phosphatase represents the primary serum ectonucleotidase after infant cardiac surgery and low post-operative alkaline phosphatase activity leads to impaired capacity to clear adenosine monophosphate. AP supplementation improves serum clearance of adenosine monophosphate to adenosine. These findings represent a potential therapeutic mechanism for alkaline phosphatase infusion during cardiac surgery. NEW AND NOTEWORTHY:We identify alkaline phosphatase (AP) as the primary soluble ectonucleotidase in infants undergoing cardiopulmonary bypass and show decreased capacity to clear AMP when AP activity decreases post-bypass. Supplementation of AP ex vivo improves this capacity and may represent the beneficial therapeutic mechanism of AP infusion seen in phase 2 studies.
| S-EPMC4934870 | biostudies-literature
Project description:1. Sulphate-dependent PP(i)-ATP exchange, catalysed by purified spinach leaf ATP sulphurylase, was correlated with the concentration of MgATP(2-) and MgP(2)O(7) (2-); ATP sulphurylase activity was not correlated with the concentration of free Mg(2+). 2. Sulphate-dependent PP(i)-ATP exchange was independent of PP(i) concentration, but dependent on the concentration of ATP and sulphate. The rate of sulphate-dependent PP(i)-ATP exchange was quantitatively defined by the rate equation applicable to the initial rate of a bireactant sequential mechanism under steady-state conditions. 3. Chlorate, nitrate and ADP inhibited the exchange reaction. The inhibition by chlorate and nitrate was uncompetitive with respect to ATP and competitive with respect to sulphate. The inhibition by ADP was competitive with respect to ATP and non-competitive with respect to sulphate. 4. ATP sulphurylase catalysed the synthesis of [(32)P]ATP from [(32)P]PP(i) and adenosine 5'-sulphatophosphate in the absence of sulphate; some properties of the reaction are described. Enzyme activity was dependent on the concentration of PP(i) and adenosine 5'-sulphatophosphate. 5. The synthesis of ATP from PP(i) and adenosine 5'-sulphatophosphate was inhibited by sulphate and ATP. The inhibition by sulphate was non-competitive with respect to PP(i) and adenosine 5'-sulphatophosphate; the inhibition by ATP was competitive with respect to adenosine 5'-sulphatophosphate and non-competitive with respect to PP(i). It was concluded that the reaction catalysed by spinach leaf ATP sulphurylase was ordered; expressing the order in the forward direction, MgATP(2-) was the first product to react with the enzyme and MgP(2)O(7) (2-) was the first product released. 6. The expected exchange reaction between sulphate and adenosine 5'-sulphatophosphate could not be demonstrated.
| S-EPMC1166247 | biostudies-other
Project description:In the presence of ATP and Mg2+, ATP sulphurylase from Saccharomyces cerevisiae catalysed the conversion of selenate into a compound with the electrophoretic and acid-lability properties of adenosine 5'-sulphatophosphate. Structural characterization, involving extensive purification of adenosine 5'-selenophosphate, proved impossible. However, we showed ATP-, Mg2+- and ATP sulphurylase-dependent, and inorganic pyrophosphatase-stimulated, production of elemental selenium from selenate in the presence of GSH (reduced glutathione). Since selenate was not reduced by GSH, this reaction proved that ATP sulphurylase had formed an active selenate. The enzyme catalysed formation of elemental selenium had the same kinetics and GSH-dependency as the non-enzymic reduction of selenite to elemental selenium by GSH. In the presence of inorganic pyrophosphatase, 2 mol of Pi was released for each mol of 'active selenate' formed. This was shown by a spectrophotometric assay for elemental selenium. The observed reactivity with thiols and the instability of the enzymic product were those predicted for selenium anhydrides. By analogy with the chemistry of sulphur, the product of the thiolytic cleavage of a selenium anhydride would be converted into selenite. The selenite would then be reduced by the thiol to elemental selenium. We conclude that ATP sulphurylase can catalyse the formation of adenosine 5'-selenophosphate. The anhydride can be reduced by thiols in a manner similar to the reduction of selenite. These results probably explain the ability of mammals, lacking a sulphate reductase system, to incorporate selenium from selenate into seleno-amino acids.
| S-EPMC1164733 | biostudies-other
Project description:1. ATP sulphurylase was purified up to 1000-fold from spinach leaf tissue. Activity was measured by sulphate-dependent [(32)P]PP(i)-ATP exchange. The enzyme was separated from Mg(2+)-requiring alkaline pyrophosphatase (which interferes with the PP(i)-ATP-exchange assay) and from other PP(i)-ATP-exchange activities. No ADP sulphurylase activity was detected. 2. Sulphate was the only form of inorganic sulphur that catalysed PP(i)-ATP exchange; K(m) (sulphate) was 3.1mm, K(m) (ATP) was 0.35mm and the pH optimum was 7.5-9.0. The enzyme was insensitive to thiol-group reagents and required either Mg(2+) or Co(2+) for activity. 3. The enzyme catalysed [(32)P]PP(i)-dATP exchange; K(m) (dATP) was 0.84mm and V (dATP) was 30% of V (ATP). Competition between ATP and dATP was demonstrated. 4. Selenate catalysed [(32)P]PP(i)-ATP exchange and competed with sulphate; K(m) (selenate) was 1.0mm and V (selenate) was 30% of V (sulphate). No AMP was formed with selenate as substrate. Molybdate did not catalyse PP(i)-ATP exchange, but AMP was formed. 5. Synthesis of adenosine 5'-[(35)S]sulphatophosphate was demonstrated by coupling purified ATP sulphurylase and Mg(2+)-dependent alkaline pyrophosphatase (also prepared from spinach) with [(35)S]sulphate and ATP as substrates; adenosine 5'-sulphatophosphate was not synthesized in the absence of pyrophosphatase. Some parameters of the coupled system are reported.
| S-EPMC1178578 | biostudies-other
Project description:1. A method of studying the free nucleotides of leaf tissue is outlined and the need for a metal ion-binding agent for the complete extraction of certain nucleotides by aqueous ethanol is established. 2. The method was used to study the effect of illumination or darkening of tobacco plants on the free nucleotides present in the chloroplast and non-chloroplast tissue components. 3. When plants that had been in the dark for a prolonged period were given 30sec. of bright light there was a rapid phosphorylation of ADP to ATP in both chloroplast and non-chloroplast components of the tissue. 4. Where plants were moved into the dark from conditions suitable for rapid photosynthesis there was a rapid conversion of ATP into AMP and the AMP was formed only in the chloroplast fraction. In continuing darkness the AMP remained restricted mainly to the chloroplast fraction for at least 2min., but eventually its concentration fell to the low value that is typical of tobacco leaves during conditions of constant illumination. If the plants were returned to the light for 30sec. the AMP was rapidly rephosphorylated.
| S-EPMC1198762 | biostudies-other
Project description:Cancer is still one of the world's most pressing health-care challenges, leading to a high number of deaths worldwide. Immunotherapy is a new developing therapy that boosts patient's immune system to fight cancer by modifying tumor-immune cells interaction in the tumor microenvironment (TME). Extracellular adenosine triphosphate (eATP) and adenosine (Ado) are signaling molecules released in the TME that act as modulators of both immune and tumor cell responses. Extracellular adenosine triphosphate and Ado activate purinergic type 2 (P2) and type 1 (P1) receptors, respectively, triggering the so-called purinergic signaling. The concentration of eATP and Ado within the TME is tightly controlled by several cell-surface ectonucleotidases, such as CD39 and CD73, the major ecto-enzymes expressed in cancer cells, immune cells, stromal cells, and vasculature, being CD73 also expressed on tumor-associated fibroblasts. Once accumulated in the TME, eATP boosts antitumor immune response, while Ado attenuates or suppresses immunity against the tumor. In addition, both molecules can mediate growth stimulation or inhibition of the tumor, depending on the specific receptor activated. Therefore, purinergic signaling is able to modulate both tumor and immune cells behavior and, consequently, the tumor-host interaction and disease progression. In this review, we discuss the role of purinergic signaling in the host-tumor interaction detailing the multifaceted effects of eATP and Ado in the inflammatory TME. Moreover, we present recent findings into the application of purinergic-targeting therapy as a potential novel option to boost antitumor immune responses in cancer.
| S-EPMC5694450 | biostudies-literature
Project description:We previously showed that the human heart expresses all known P2X and P2Y receptors activated by extra-cellular adenine or uracil nucleotides. Despite evidence that, both in humans and rodents, plasma levels of ATP and UTP markedly increase during myocardial infarction, the differential effects mediated by the various adenine- and uracil-preferring myocardial P2 receptors are still largely unknown. Here, we studied the effects of adenine and uracil nucleotides on murine HL-1 cardiomyocytes. RT-PCR analysis showed that HL-1 cardiomyocytes express all known P2X receptors (except for P2X(2)), as well as the P2Y(2,4,6,14) subtypes. Exposure of cardiomyocytes to adenine nucleotides (ATP, ADP or BzATP) induced apoptosis and necrosis, as determined by flow-cytometry. Cell death was exacerbated by tumour necrosis factor (TNF)-alpha, a cytokine implicated in chronic heart failure progression. Conversely, uracil nucleotides (UTP, UDP and UDPglucose) had no effect 'per se', but fully counteracted the deleterious effects induced by adenine nucleotides and TNF-alpha, even if added to cardiomyocytes after beginning exposure to these cell death-inducing agents. Thus, exposure of cardiomyocytes to elevated concentrations of ATP or ADP in the presence of TNF-alpha contributes to cell death, an effect which is counteracted by uracil-preferring P2 receptors. Cardiomyocytes do not need to be 'primed' by uracil nucleotides to become insensitive to adenine nucleotides-induced death, suggesting the existence of a possible 'therapeutic' window for uracil nucleotides-mediated protection. Thus, release of UTP during cardiac ischaemia and in chronic heart failure may protect against myocardial damage, setting the basis for developing novel cardioprotective agents that specifically target uracil-preferring P2Y receptors.
| S-EPMC3822540 | biostudies-literature
Project description:1. Human platelet-rich plasma prelabelled with [(3)H]adenine was incubated at 37 degrees C with antimycin A and 2-deoxy-d-glucose. Variations in the amounts of ATP, ADP and P(i), and in the radioactivity of ATP, ADP, AMP, IMP, hypoxanthine+inosine and adenine were determined during incubation. Adrenaline- and ADP-induced platelet aggregation and the ADP-induced shape change of the platelets were determined concurrently. 2. 2-Deoxyglucose caused conversion of [(3)H]ATP to [(3)H]hypoxanthine+inosine. The rate of this conversion increased with increasing 2-deoxyglucose concentration and was markedly stimulated by addition of antimycin, which had no effect alone. At maximal ATP-hypoxanthine conversion rates, the IMP radioactivity remained at values tenfold higher than control, whereas [(3)H]ADP and [(3)H]AMP radioactivity gave variations typical for product/substrates in consecutive reactions. The specific radioactivityof ethanol-soluble platelet ATP decreased during incubation to less than one-tenth of its original value. The amounts and radioactivity of ethanol-insoluble ADP did not vary during incubation with the metabolic inhibitors. 3. The rate of ADP- and adrenaline-induced primary aggregation decreased as the amount of radioactive ATP declined, and complete inhibition of aggregation was obtained at a certain ATP concentration (metabolic ATP threshold). This threshold decreased with increasing concentration of inducer ADP. 4. Secondary platelet aggregation (release reaction) had a metabolic ATP threshold markedly higher than that of primary aggregation. 5. Shape change was gradually inhibited as the ATP radioactivity decreased, and had a metabolic ATP threshold distinctly lower than that of primary aggregation, and which decreased with increasing concentration of ADP. 6. A small but distinct fraction of [(3)H]ATP disappeared rapidly during the combined shape change-aggregation process induced by ADP in platelets incubated with metabolic inhibitors, whereas no ATP disappearance occurred during aggregation in their absence.
| S-EPMC1168507 | biostudies-other