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PubMed1971

Effects of increased heart work on glycolysis and adenine nucleotides in the perfused heart of normal and diabetic rats.

1. In the isolated perfused rat heart, the contractile activity and the oxygen uptake were varied by altering the aortic perfusion pressure, or by the atrial perfusion technique (;working heart'). 2. The maximum increase in the contractile activity brought about an eightfold increase in the oxygen uptake. The rate of glycolytic flux rose, while tissue contents of hexose monophosphates, citrate, ATP and creatine phosphate decreased, and contents of ADP and AMP rose. 3. The changes in tissue contents of adenine nucleotides during increased heart work were time-dependent. The ATP content fell temporarily (30s and 2min) after the start of left-atrial perfusion; at 5 and 10min values were normal; and at 30 and 60min values were decreased. ADP and AMP values were increased in the first 15min, but were at control values 30 or 60min after the onset of increased heart work. 4. During increased heart work changes in the tissue contents of adenine nucleotide and of citrate appeared to play a role in altered regulation of glycolysis at the level of phosphofructokinase activity. 5. In recirculation experiments increased heart work for 30min was associated with increased entry of [(14)C]glucose (11.1mm) and glycogen into glycolysis and a comparable increase in formation of products of glycolysis (lactate, pyruvate and (14)CO(2)). There was no major accumulation of intermediates. Glycogen was not a major fuel for respiration. 6. Increased glycolytic flux in Langendorff perfused and working hearts was obtained by the addition of insulin to the perfusion medium. The concomitant increases in the tissue values of hexose phosphates and of citrate contrasted with the decreased values of hexose monophosphates and of citrate during increased glycolytic flux obtained by increased heart work. 7. Decreased glycolytic flux in Langendorff perfused hearts was obtained by using acute alloxan-diabetic and chronic streptozotocin-diabetic rats; in the latter condition there were decreased tissue contents of hexose phosphates and of citrate. There were similar findings when working hearts from streptozotocin-diabetic rats with insulin added to the medium were compared with normal hearts. 8. The effects of insulin addition or of the chronic diabetic state could be explained in terms of an action of insulin on glucose transport. Increased heart work also acted at this site, but in addition there was evidence for altered regulation of glycolysis mediated by changes in tissue contents of adenine nucleotides or of citrate.

Adenine Nucleotides↗
PubMed1972

The relation of sodium and potassium ion transport to the respiration and adenine nucleotide content of liver slices treated with inhibitors of respiration.

1. The dependence of the net transport of Na(+) and K(+) by rat liver on the respiration has been determined by incubating slices in the presence of varying concentrations of respiratory inhibitors. 2. Neither the rate of net transport nor the total amount of each ion transported was inhibited unless the rate of endogenous respiration was decreased below a critical value of about 330mmol of O(2)/h per kg of protein (i.e. 50% of the total endogenous respiration). 3. The uninhibited rate of respiration could be varied over a twofold range (380-770mmol of O(2)/h per kg of protein) by the use of different substrates, but the critical value for the onset of transport inhibition was quite constant (290-360mmol/h per kg of protein) under these different conditions. 4. Slices incubated at 38 degrees C without inhibitors showed an increase of their ATP content and the concentration ratio ATP/ADP. The final ATP content and concentration ratio, ATP/ADP, of slices treated with different concentrations of inhibitors were closely related to the rate of respiration. 5. The increased ATP content of the control slices during incubation was equal to the increase of total adenine nucleotides. At increasing degrees of respiratory inhibition the relative contributions of ADP and AMP to the total adenine nucleotide content increased. 6. The critical rate of respiration for the onset of inhibition of ion transport and the corresponding contents of adenine nucleotides provide estimates of the maximal values of certain parameters of energy metabolism required for the support of alkali-cation transport in the liver slices.

Adenine Nucleotides↗
PubMed1977

Alterations in nicotinamide and adenine nucleotide systems during mixed-function oxidation of p-nitroanisole in perfused livers from normal and phenobarbital-treated rats.

The contents of adenine nucleotides as well as steady-state concentrations of a number of glycolytic, pentose phosphate-pathway and tricarboxylic acid-cycle intermediates were measured in extracts of livers from normal and phenobarbital-treated rats that were perfused with p-nitroanisole. Metabolites were measured in livers that were freeze-clamped during periods of maximal rates of drug metabolism. Treatment of rats with phenobarbital increased rates of p-nitroanisole O-demethylation approx. fivefold. The concentrations of lactate, xylulose 5-phosphate and ribulose 5-phosphate were increased by phenobarbital treatment, whereas that of fructose 1,6-bisphosphate declined. Perfusion of livers with p-nitroanisole produced significant increases in 6-phosphogluconate and ribulose 5-phosphate in livers from phenobarbital-treated rats, but not in livers from control rats. Treatment of rats with phenobarbital caused [NADP(+)]/[NADPH] to change in the direction of more oxidation, as calculated from measured concentrations of 6-phosphogluconate and ribulose 5-phosphate; however, the [NADP(+)]/[NADPH] ratio calculated from ;malic' enzyme was not changed. Additions of p-nitroanisole produced a reduction of NADP(+) as calculated from 6-phosphogluconate dehydrogenase activity, but did not alter the [NADP(+)]/[NADPH] ratio calculated from substrates assumed to be in equilibrium with ;malic' enzyme. Activities of both glucose 6-phosphate dehydrogenase and ;malic' enzyme were increased by phenobarbital treatment. NAD(+) became more reduced as a result of phenobarbital treatment; however, perfusion of livers with p-nitroanisole did not cause a change in the oxidation-reduction state of this nucleotide. Concentrations of adenine nucleotides in livers were not altered significantly by treatment of rats with phenobarbital; however, a significant decline in the [ATP]/[ADP] ratio occurred during mixed-function oxidation of p-nitroanisole in livers from phenobarbital-treated rats, but not in livers from normal rats. Perfusion of livers with two other substrates for mixed-function oxidation, hexobarbital and aminopyrine, produced an increase in the [NADP(+)]/[NADPH] ratio calculated from ;malic' enzyme. In contrast with livers perfused with p-nitroanisole, there was no significant change in adenine nucleotides in livers exposed to hexobarbital or aminopyrine. Addition of 2,4-dinitrophenol (25mum) to the perfusate containing aminopyrine decreased the [ATP]/[ADP] ratio and tended to prevent the oxidation of NADPH observed with aminopyrine alone. Thus in the presence of an uncoupler of oxidative phosphorylation, NADPH generation may exceed its utilization via mixed-function oxidation.

Adenine Nucleotides↗
PubMed1994

Incorporation of bisphosphonates into adenine nucleotides by amoebae of the cellular slime mould Dictyostelium discoideum.

Bisphosphonates are a class of synthetic pyrophosphate analogues. Some are known to be potent inhibitors of osteoclast-mediated bone resorption in vivo, but their mechanisms of action are unclear. The order of potency of bisphosphonates as inhibitors of bone resorption closely matches the order of potency as inhibitors of growth of amoebae of the slime mould Dictyostelium discoideum, indicating that bisphosphonates may have a mechanism of action that is similar in both osteoclasts and Dictyostelium. Methylenebisphosphonate and several halogenated derivatives, which have low potency as antiresorptive agents and as growth inhibitors of Dictyostelium, are metabolized intracellularly by Dictyostelium amoebae into methylene-containing adenine nucleotides. We have used a combination of n.m.r. and f.p.l.c. analysis to determine whether incorporation into nucleotides is a feature of other bisphosphonates, especially those that are potent antiresorptive agents. Only bisphosphonates with short side chains or of low potency are incorporated into adenine nucleotides, whereas those with long side chains or of high potency are not metabolized. Bisphosphonate metabolism in cell-free extracts of Dictyostelium was accompanied by inhibition of aminoacylation of tRNA by several aminoacyl-tRNA synthetases. These enzymes were barely affected by the bisphosphonates that were not metabolized. The results indicate that some bisphosphonates are not metabolically inert analogues of pyrophosphate and appear to be metabolized by aminoacyl-tRNA synthetases. The cellular effects of some bisphosphonates may be the result of their incorporation into adenine nucleotides or inhibition of aminoacyl-tRNA synthetases, although the potent bisphosphonates appear to act by a different mechanism.

Adenine Nucleotides↗
PubMed1997

Tight links between adenine and guanine nucleotide pools in mouse pancreatic islets: a study with mycophenolic acid.

Glucose metabolism in pancreatic B-cells leads to an increase in the ATP/ADP ratio that might participate in the regulation of insulin secretion. Good correlations have also been observed between guanine nucleotide levels in isolated pancreatic islets and insulin secretion. To assess whether guanine nucleotides have a specific role in stimulus-secretion coupling, their concentration should be modified selectively. This was attempted by culturing mouse islets overnight in the presence of mycophenolic acid (MPA), an inhibitor of GMP synthesis at the level of IMP dehydrogenase. The drug (25-50 microg/ml) did not affect the insulin content but decreased the GTP content of the islets and inhibited insulin secretion during subsequent incubation in the presence of 15 mM glucose. However, MPA also decreased the ATP/ADP ratio in the islets. The addition of guanine to the culture medium (to stimulate the salvage pathway of GTP synthesis) restored normal GTP levels, corrected the ATP/ADP ratio and partly prevented the inhibition of insulin release. In contrast, attempts to stimulate ATP synthesis specifically (by provision of adenine or adenosine) failed to reverse any of the effects of MPA. It is concluded that guanine and adenine nucleotide pools are tightly linked and cannot be specifically affected by MPA in pancreatic islet cells, probably because of the activity of nucleoside diphosphate kinase and because of the role of GTP in several reactions leading to adenine nucleotide generation. Contrary to previous claims, MPA is not an adequate tool for evaluating a specific role of guanine nucleotides in the control of insulin secretion.

Adenine Nucleotides↗
PubMed2000

The archaeal halophilic virus-encoded Dam-like methyltransferase M. phiCh1-I methylates adenine residues and complements dam mutants in the low salt environment of Escherichia coli.

The genome of the archaeal virus phiCh1, infecting Natrialba magadii (formerly Natronobacterium magadii), is composed of 58.5 kbp linear ds DNA. Virus particles contain several RNA species in sizes of 100-800 nucleotides. A fraction of phiCh1 genomes is modified within 5'-GATC-3' and related sequences, as determined by various restriction enzyme digestion analyses. High performance liquid chromatography revealed a fifth base, in addition to the four nucleosides, which was identified as N6-methyladenosine. Genetic analyses and subsequent sequencing led to the identification of a DNA (N6-adenine) methyltransferase (mtase) gene. The protein product was designated M.phiCh1-I. By the localization of the most conserved motifs (a DPPY motif occurring before FxGxG), the enzyme was placed within the beta-subgroup of the (N6-adenine) methyltransferase class. The mtase gene of phiCh1 was classified as a 'late' gene, as determined by measuring the kinetics of mRNA and protein expression in N. magadii during the lytic cycle of phiCh1. After infection of cells, M.phiCh1-I mRNA and protein could be detected in lower amounts than in the situation of virus induction from lysogenic cells. Consequently, only about 5% of the phiCh1 progeny genomes after infection of N. magadii carry the M.phiCh1-I methylation in contrast to 50% of virus genomes generated by induction of phiCh1-lysogenic N. magadii cells. Heterologous expression of the mtase from a halophile with 3 M cytoplasmic salt concentration showed an unexpected feature: the protein was active in the low environment of Escherichia coli and was able to methylate DNA in vivo. Interestingly, it seemed to exhibit a higher sequence specificity in E. coli that resulted in adenine methylation exclusively in the sequence 5'-GATC-3'. Additionally, expression of M.phiCh1-I in dam- E. coli cells led to a complete substitution of the function of M. Dam in DNA mismatch repair.

Amino Acid Sequence↗
PubMed1996

A second form of adenine phosphoribosyltransferase in Arabidopsis thaliana with relative specificity towards cytokinins.

Adenine phosphoribosyltransferase (APRTase) is an important enzyme for its ability to convert adenine, a byproduct of many biochemical reactions, into AMP. By functional complementation of an Escherichia coli mutant, cDNAs encoding two APRTases have been cloned from Arabidopsis thaliana. One of the cDNAs (ATapt1) has been previously identified while the second (ATapt2) is of a previously unknown type. Kinetic analysis of the two enzymes purified from E. coli expressing the two cDNAs indicates that ATapt2 has a higher affinity for cytokinin than the ATapt1. RNase protection studies indicate that the ATapt2, is not expressed in leaves. Analysis of the gene structure indicates that ATapt2 has identical intron positions to ATapt1, but neither the intron sequence nor intron size are conserved between the two genes. The implications of a second, differentially expressed APRTase with affinity for both adenine and cytokinin are discussed.

Adenine Phosphoribosyltransferase↗
PubMedDate not supplied

In vitro metabolism of packed erythrocytes stored in CPD-adenine.

In vitro metabolism of erythrocytes packed at 70 and 90 per cent hematocrits and stored in various CPD-adenine preservatives was studied. It was found that maintenance of acceptable levels of adenosine triphosphate (ATP) for the full 42 days of storage could be accomplished only if glucose levels were doubled from the standard 138.7 mM concentration to 277.5 mM level. If glucose levels were doubled, the amount of adenine could be decreased from 4.07 mM (0.50 mM final concentration) to 2.04 mM (0.25 mM final concentration) with maintenance of ATP at greater than 2.0 mumoles/g Hb. 2,3-diphosphoglycerate concentrations were essentially absent by 21 days in the various media studies. Thus, in vitro levels of ATP appear to be maintained at acceptable levels in a CPD media modified to contain 2 times glucose and 2.04 mM adenine.

Adenine↗
PubMedDate not supplied

Blood storage XXII. Improvement in red blood cell 2,3-DPG levels at six weeks by 20 mM PO4 in CPD-adenine-inosine.

Inorganic phosphate has been known to assist red blood cell maintenance of ATP and in the presence of inosine to assist in the maintenance of 2,3-DPG. High concentrations of phosphate, while helping ATP maintenance, were found to be deleterious to 2,3-DPG maintenance in CPD-adenine preservatives. However, in the presence of inosine, concentrations of phosphate as high as 10 mM were advantageous to 2,3-DPG maintenance. The present study extends the observations on ATP and 2,3-DPG maintenance in CPD-adenine-inosine preservatives from the previous 10 mM to 20 mM phosphate. A high phosphate (20 mM) effect has been seen as improved maintenance of 2,3-DPG levels during the fifth and sixth weeks of storage of whole blood at 4C. This supports the previously reported observation of improved maintenance of 2,3-DPG in a 10 mM phosphate preservative. This is ten times the 2 mM phosphate concentration in CPD-adenine. In the low phosphate preservative (2 mM), 2,3-DPG maintenance is less than that in all of the higher phosphate preservatives after the second week of storage. ATP concentrations in this experiment show good maintenance throughout six weeks of storage.

Adenine↗
PubMedDate not supplied

Blood storage XXIV: red blood cell 2,3-DPG and ATP maintenance for six weeks in CPD-adenine with higher phosphate, pyruvate, and dihydroxyacetone.

The individual and collective effects of various phosphate, pyruvate and dihydroxyacetone concentrations on 2,3-DPG and ATP maintenance during blood storage with CPD-adenine (0.25 mM), were studied. Phosphate concentrations ranged from 2 to 100 mM. Low concentations were best for 2,3-DPG maintenance during the first three weeks, after which there was no difference. ATP concentrations were better maintained by the highest phosphate concentrations in the first week. After the second week the lower concentrations of phosphate were better. With pyruvate 40 and 60 mM were the best for 2,3-DPG levels through six weeks of storage. ATP concentrations were poorest with high pyruvate. Maintenance of 2,3-DPG was above half normal for six weeks of storage in the 60, 80 and 100 mM DHA preservatives. ATP concentrations were best maintained in the preservative lacking DHA. Combinations of phosphate, pyruvate and DHA in concentrations which had been found to be effective when used individually were studied. Best maintenance of 2,3-DPG (above half normal levels) for six weeks was afforded by pyruvate, phosphate and DHA, and by pyruvate and DHA. ATP maintenance was best afforded by CPD-adenine alone and CPD-adenine with pyruvate and phosphate. Pyruvate alone maintained ATP less well and the pyruvate-DHA was worst. Intermediate in maintenance of ATP was the preservative containing pyruvate, phosphate and DHA.

Adenine↗
PubMedDate not supplied

The in vivo survival of red blood cells stored in modified CPD with adenine: report of a multi-institutional cooperative effort.

In order to provide data in support of licensure applications for citrate-phosphate-dextrose (CPD) supplemented with adenine, a multi-institutional cooperative effort was organized to determine survivability of red blood cells subjected to prolonged liquid storage. Two manufacturers supplied plastic multiple bag blood storage containers prefilled with modified CPD (glucose 25% greater than the normal concentration) supplemented with adenine (17.0 to 17.3 mg per 63 ml of anticoagulant; 0.25 millimolar approximate final concentration when diluted with 450 ml of whole blood for 35 days showed a mean survival of 80.53 +/- 6.44 per cent (1 SD). Both red blood cell and supernatant plasma biochemical characteristics were comparable to those reported for whole blood stored for 21 days in either acid-citrate-dextrose (ACD) or CPD. Red blood cells from 19 units stored as concentrates for 35 days (Hct 75.03 +/- 3.74%) had a mean survival of 71.38 +/- 10.3 per cent with considerable interdonor variation in survival and interlaboratory variation in some biochemical characteristics. Red blood cells from eight units stored as concentrates (Hct 75.38 +/- 4.30%) for 28 days showed a mean survival of 83.97 +/- 6.10 per cent and biochemical characteristics comparable to those reported for red blood cell concentrates stored in CPD or ACD for 21 days. Modified CPD with adenine as formulated offers an improved anticoagulant for blood banking by extending the permissible red blood cell storage period.

Adenine↗
PubMedDate not supplied

Platelet glycolysis in platelet storage. IV. The effect of supplemental glucose and adenine.

Platelet concentrates were prepared from blood collected in CPD, CPD-A1, and CPD-A3. CPD-A1 contains 1.25 times as much glucose as does CPD, and sufficient adenine to provide a final concentration of 0.25 mM; CPD-A3 contains twice as much glucose as does CPD, and sufficient adenine to provide a final concentration of 0.5 mM. The consumption of glucose and the production of lactate and pyruvate in the platelet concentrates during room temperature storage was not influenced by glucose or adenine concentration. There was no difference in the rates of fall of the pH of platelets collected in the three preservatives. However, the number of contaminating white blood cells had a significant effect on these parameters. It is suggested that minimizing the number of contaminating white blood cells in platelet preparations may prove to be an important factor in platelet preservation.

Adenine↗
PubMedDate not supplied

The in vitro evaluation of modifications in CPD-adenine anticoagulated-preserved blood at various hematocrits.

Erythrocytes stored in the new CPD-adenine anticoagulant (CPDA-1) barely met the 70 per cent 24-hour postinfusion 51Cr recoveries on day 35 when stored at hematocrit greater than or equal to 75 per cent. CPDA-1 differs from CPD in that it has 1.25 times the glucose concentration plus 17.3 mg adenine/63 ml. In an effort to improve the survivability (or viability) of red blood cells following extended storage (35+ days), two new CPD-adenine anticoagulants have been tested in vitro. CPDA-2 and CPDA-3 (both of which contain 34.6 mg/63 ml of anticoagulant or 0.50 mM adenine [final blood concentration], and either 1.75 times or 2.0 times respectively the amount of glucose used in CPD) have been tested for whole blood or red blood cell storage to 42 days. Red blood cell ATP concentrations were better maintained throughout 42 days of storage in both of these formulations than in CPDA-1 at hematocrits that ranged from 40 to 85. Other biochemical parameters (2,3-DPG, pH, plasma hemoglobin) were similar to those of blood stored in CPD or CPDA-1.

Adenine↗
PubMedDate not supplied

Preservation of neutrophils in CPD-adenine.

Human neutrophils were stored in vitro in CPD or CPD-adenine plasma under conditions designed to simulate those of leukapheresis followed by short-term preservation. Viability, morphology by light microscopy, and phagocytic ability of cells stored in either anticoagulant were similar when studied sequentially during 72 hours of storage. Thus, CPD-adenine offered no advantage, under the conditions employed, over standard CPD without adenine.

Adenine↗
PubMedDate not supplied

Improved red blood cell storage using optional additive systems (OAS) containing adenine, glucose and ascorbate-2-phosphate.

Red blood cells were treated with optional additive system (OAS) solutions to provide component-specific metabolic enhancement for improved storage. Red blood cell viability, as monitored by ATP concentrations, was maintained by use of adenine and extra glucose. Red blood cell oxygen offloading characteristics were improved by maintenance of red blood cell 2,3-DPG concentrations with ascorbate-2-phosphate (AsP). The use of CPD-collected red blood cells with an OAS containing adenine, glucose, and AsP, or CPD-adenine collected red blood cells with an OAS containing AsP demonstrates the potential to store red blood cells at least 42 days and to maintain red blood cell 2,3-DPG.

2,3-Diphosphoglycerate↗
PubMed1999

Adenine-nucleotide binding sites on the inositol 1,4,5-trisphosphate receptor bind caffeine, but not adenophostin A or cyclic ADP-ribose.

Binding of ATP to the inositol 1,4,5-trisphosphate receptor (IP3R) results in a more pronounced Ca2+ release in the presence of inositol 1,4,5-trisphosphate (IP3). We have expressed the cDNAs encoding two putative adenine-nucleotide binding sites of the neuronal form of IP3R-1 as glutathione S-transferase (GST)-fusion proteins in bacteria. Specific [alpha-32P]ATP binding was observed for the two GST-fusion proteins, representing aa 1710-1850 and aa 1944-2040 of IP3R-1. The ATP-binding sites in both fusion proteins had the same nucleotide specificity as found for the intact IP3R (ATP > ADP > AMP > GTP). Smaller GST-fusion proteins (aa 1745-1792 and aa 2005-2023) displayed a much weaker ATP-binding activity. CoA, which also potentiated IP3-induced Ca2+ release in A7r5 cells, interacted with the ATP-binding sites on the fusion proteins. Such interaction was not observed for 1,N6-etheno CoA and 3'-dephospho-CoA, which are much less effective in potentiating IP3-induced Ca2+ release. Since the adenine-containing compounds adenophostin A, caffeine and cyclic ADP-ribose modulate IP3-induced Ca2+ release, a possible effect of these compounds on the ATP-binding sites was examined. ATP stimulated adenophostin A- and IP3-induced Ca2+ release in A7r5 cells with an EC50 of respectively 21 and 20 microM. Also the threshold concentration of ATP for stimulating the release was similar for the two agonists. Adenophostin A (100 microM) and cyclic ADP-ribose (100 microM) were ineffective in displacing [alpha-32P]ATP from the binding sites of both GST-fusion proteins. Caffeine (50 mM), however, inhibited [alpha-32P]ATP binding to both fusion proteins by more than 50%. These data provide evidence for a direct interaction of caffeine but not of adenophostin A or cyclic ADP-ribose with the adenine-nucleotide binding sites of the IP3R.

Adenine↗
PubMed1990

Adenine nucleotide degradation in striated muscle.

Adenine nucleotides play a central role in cellular processes involving the transduction of energy. Among striated muscles, the management of adenine nucleotide catabolism differs greatly. These differences can be understood by considering the distribution, activity, and kinetic characteristics of degradative enzymes. When these factors are weighed in light of the differing energetic demands faced by heart and skeletal muscle fiber types, a coherent picture emerges. Our analysis suggests that, as the routine energy demand of a particular muscle rises in relation to the tissue's capacity for oxidative metabolism, the pattern of adenine nucleotide degradation shifts toward increased rates of AMP deamination along with lessened rates of dephosphorylation.

5'-Nucleotidase↗
PubMed1990

Adenine nucleotide depletion in human muscle during exercise: causality and significance of AMP deamination.

The predominant route for adenine nucleotide catabolism in skeletal muscle is deamination of AMP to inosine monophosphate (IMP) and ammonia (NH3). Deamination of AMP is enhanced during exercise when the capacity to rephosphorylate ADP is impaired. Thus, in human muscle the formation of IMP (NH3) during exercise is augmented under the following conditions (1) at high intensities, (2) during beta-adrenoceptor blockade, (3) during hypoxia, (4) after detraining, and (5) at low glycogen levels. The formation of IMP is related to the metabolic stress (as indicated by the degree of phosphocreatine breakdown and lactate accumulation), the rate of ATP turnover, and the fiber type composition. During maximal exercise at 100% of VO2max or sustained isometric contractions to fatigue, about 15% of the adenine nucleotide (AN) pool is degraded through deamination of AMP to IMP. It is suggested that the stimulus for increased AMP deamination is increased transient levels of ADP and AMP in the contracting muscle fiber. Deamination of AMP to IMP and NH3 provides a sink for ADP, whereby the ATP/ADP ratio and the phosphorylation potential are kept high, which may be essential for the continuation of the contraction process. This implies that the relative levels of the adenine nucleotides are more important for maintenance of adequate cellular function than the absolute concentration of ATP.

AMP Deaminase↗