scholarly journals Biochemical and physiological investigations on adenosine 5’ monophosphate deaminase from Plasmodium spp.

2018 ◽  
Author(s):  
Lakshmeesha Kempaiah Nagappa ◽  
Hemalatha Balaram
Keyword(s):  
Energy Homeostasis ◽  
Purine Nucleoside Phosphorylase ◽  
Energy Charge ◽  
Adenylate Energy Charge ◽  
Amp Deaminase ◽  
Inosine Monophosphate Dehydrogenase ◽  
Inosine Monophosphate ◽  
Adenylosuccinate Lyase ◽  
Adenylosuccinate Synthetase ◽  
A Cell

Abbreviations:HGXPRT - Hypoxanthine-guanine-xanthine phosphoribosyltransferase, ADSS - Adenylosuccinate synthetase, ASL - Adenylosuccinate lyase, GMPS - Guonosine monophosphate synthetase, IMPDH - Inosine monophosphate dehydrogenase, ISN1 - Inosine monophosphate specific nucleotidase, PNP - Purine nucleoside phosphorylaseSummaryInterplay between ATP generating and utilizing pathways in a cell is responsible for maintaining cellular ATP/energy homeostasis that is reflected by Adenylate Energy Charge (AEC) ratio. Adenylate kinase (AK), that catalyzes inter-conversion of ADP, ATP and AMP, plays a major role in maintaining AEC, and is regulated by cellular AMP levels. Hence, the enzymes AMP deaminase (AMPD) and nucleotidases, which catabolize AMP, indirectly regulate AK activity and in-turn affect AEC. Here, we present the first report on AMPD from Plasmodium, the causative agent of malaria. The recombinant enzyme expressed in Saccharomyces cerevisiae was studied using functional complementation assay and residues vital for enzyme activity have been identified. Similarities and differences between Plasmodium falciparum AMPD (PfAMPD) and its homologs from yeast, Arabidopsis and humans are also discussed. The AMPD gene was deleted in the murine malaria parasite P. berghei and was found to be non-essential for intra-erythrocytic growth of the knockout parasites. However, when episomal expression was attempted, viable parasites were not obtained, suggesting that perturbing AMP homeostasis by over-expressing AMPD might be lethal. As AMPD is known to be allosterically modulated by ATP, GTP and phosphate, allosteric activators of PfAMPD could be developed as anti-parasitic agents.

Control of AMP deaminase 1 binding to myosin heavy chain

1998 ◽  
Vol 275 (3) ◽  
pp. C870-C881 ◽  
Author(s):  
Ichiro Hisatome ◽  
Takayuki Morisaki ◽  
Hiroshi Kamma ◽  
Takako Sugama ◽  
Hiroko Morisaki ◽  
...  
Keyword(s):  
Myosin Heavy Chain ◽  
Heavy Chain ◽  
Sequence Similarity ◽  
Critical Role ◽  
Energy Charge ◽  
Adenylate Energy Charge ◽  
Amp Deaminase ◽  
Amino Terminal

AMP deaminase (AMPD) plays a central role in preserving the adenylate energy charge in myocytes following exercise and in producing intermediates for the citric acid cycle in muscle. Prior studies have demonstrated that AMPD1 binds to myosin heavy chain (MHC) in vitro; binding to the myofibril varies with the state of muscle contraction in vivo, and binding of AMPD1 to MHC is required for activation of this enzyme in myocytes. The present study has identified three domains in AMPD1 that influence binding of this enzyme to MHC using a cotransfection model that permits assessment of mutations introduced into the AMPD1 peptide. One domain that encompasses residues 178–333 of this 727-amino acid peptide is essential for binding of AMPD1 to MHC. This region of AMPD1 shares sequence similarity with several regions of titin, another MHC binding protein. Two additional domains regulate binding of this peptide to MHC in response to intracellular and extracellular signals. A nucleotide binding site, which is located at residues 660–674, controls binding of AMPD1 to MHC in response to changes in intracellular ATP concentration. Deletion analyses demonstrate that the amino-terminal 65 residues of AMPD1 play a critical role in modulating the sensitivity to ATP-induced inhibition of MHC binding. Alternative splicing of the AMPD1 gene product, which alters the sequence of residues 8–12, produces two AMPD1 isoforms that exhibit different MHC binding properties in the presence of ATP. These findings are discussed in the context of the various roles proposed for AMPD in energy production in the myocyte.

Enzymatic Properties of 5′-AMP Deaminase in Platelet Lysates

1977 ◽  
Vol 37 (03) ◽  
pp. 380-395 ◽  
Author(s):  
H Holmsen ◽  
A.-C Østvold ◽  
M. A Pimentel
Keyword(s):  
Heavy Metals ◽  
Resting State ◽  
Human Platelet ◽  
Energy Charge ◽  
Maximal Activity ◽  
Monovalent Cation ◽  
Adenylate Energy Charge ◽  
Amp Deaminase ◽  
Optimal Activity ◽  
Competitive Inhibitors

SummaryMetabolic ATP is converted to hypoxanthine during platelet secretion, metabolic shock and slowly in the resting state. This conversion involves deamination of 5′-AMP to 5′-IMP which has been studied by incubating 5′-AMP (3–40 μM) with human platelet lysates and quantifying the metabolites formed. Deamination occurred only when EDTA was present or endogenous ATP absent, showing that 5’-AMP deaminase (EC 3.5.4.6) was the only enzyme attacking AMP. EDTA stimulated AMP deamination, probably by removal of endogenous heavy metals which were powerful inhibitors of deamination. The experiments were therefore performed with EDTA. 5′-AMP deaminase was soluble, and had optimal activity at pH 6.5; however, the rate of AMP deamination was highly dependent on the type of buffer used. Km was 0.92 × 10–3M and Vmax was 0.26 μmoles/min x mg protein. The deamination required presence of monovalent cation with Li+ = Na+ >K+ >NH4 +, a sequence distinctly different from that seen with erythrocyte and muscle deaminase. 50 mM Na+ gave maximal activity with [math]. Tris+ and K+ were competitive inhibitors with respect to Na+, a feature not reported for the enzyme from other tissues. Above 60 mM K+ there was no effect by Na+ (0–100 mM). PPi, GTP, ITP, CTP and UTP gave greater inhibition than Pi and phospho-esters. Unlike AMP deaminase from other tissues, the platelet enzyme was insensitive to fluoride. ATP counteracted Pi and GTP inhibition and activated with or without Na+; ATP-and Na+-activation were additive. The activity increased as the adenylate energy charge was lowered, but was linearly related to the AMP concentration, thus in sharp contrast to deaminase from the liver. It is suggested that in the intact platelet AMP deamination is regulated chiefly through variations in the AMP level and not likely through variations in the ATP/Pi ratio.

AMP deaminase deficiency: Study of the human skeletal muscle purine metabolism during ischaemic isometric exercise

1987 ◽  
Vol 72 (4) ◽  
pp. 475-482 ◽  
Author(s):  
S. P. T. Sinkeler ◽  
R. A. Binkhorst ◽  
E. M. G. Joosten ◽  
R. A. Wevers ◽  
M. M. Coerwinkel ◽  
...  
Keyword(s):  
Skeletal Muscle ◽  
Exercise Test ◽  
Adenine Nucleotide ◽  
Energy Charge ◽  
Isometric Exercise ◽  
Creatine Phosphate ◽  
Adenylate Energy Charge ◽  
Amp Deaminase ◽  
Control Subjects ◽  
Before And After

1. Muscle biopsies were taken from 10 control subjects and five AMP deaminase (AMPD) deficient individuals before and after an ischaemic isometric exercise test and analysed for purine nucleotide, NAD+, creatine phosphate (CP) and lactate content. 2. The decrease of ATP induced by the exercise test was significantly lower in the AMPD deficient patients than in the controls, but the decrease of creatine phosphate and the increase of lactate did not differ. There were no significant differences in the exertional performance level between patients and controls and no evidence was obtained of an increased energy expenditure per unit of performance in AMPD deficiency. 3. The AMPD deficient individuals were equally capable of maintaining a high adenylate energy charge (EC) as the control subjects, which indicates a normal regulation of the balance between ATP consumption and ATP regeneration. 4. ATP, ADP and total adenine nucleotide (TAN) but not AMP, were significantly elevated in the AMPD deficient patients as compared with the controls before as well as after the exercise test. This underlines the role of AMPD activity in the adenine nucleotide catabolism of skeletal muscle.

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