scholarly journals Magnesium Signaling in Plants

2021 ◽  
Vol 22 (3) ◽  
pp. 1159
Author(s):  
Leszek A. Kleczkowski ◽  
Abir U. Igamberdiev
Keyword(s):  
Equilibrium Constant ◽  
Adenylate Kinase ◽  
Nucleoside Diphosphate Kinase ◽  
Phloem Loading ◽  
Photosynthetic Performance ◽  
Fine Tuning ◽  
Primary Control ◽  
Membrane Bound ◽  
Free Magnesium ◽  
Apparent Equilibrium

Free magnesium (Mg2+) is a signal of the adenylate (ATP+ADP+AMP) status in the cells. It results from the equilibrium of adenylate kinase (AK), which uses Mg-chelated and Mg-free adenylates as substrates in both directions of its reaction. The AK-mediated primary control of intracellular [Mg2+] is finely interwoven with the operation of membrane-bound adenylate- and Mg2+-translocators, which in a given compartment control the supply of free adenylates and Mg2+ for the AK-mediated equilibration. As a result, [Mg2+] itself varies both between and within the compartments, depending on their energetic status and environmental clues. Other key nucleotide-utilizing/producing enzymes (e.g., nucleoside diphosphate kinase) may also be involved in fine-tuning of the intracellular [Mg2+]. Changes in [Mg2+] regulate activities of myriads of Mg-utilizing/requiring enzymes, affecting metabolism under both normal and stress conditions, and impacting photosynthetic performance, respiration, phloem loading and other processes. In compartments controlled by AK equilibrium (cytosol, chloroplasts, mitochondria, nucleus), the intracellular [Mg2+] can be calculated from total adenylate contents, based on the dependence of the apparent equilibrium constant of AK on [Mg2+]. Magnesium signaling, reflecting cellular adenylate status, is likely widespread in all eukaryotic and prokaryotic organisms, due simply to the omnipresent nature of AK and to its involvement in adenylate equilibration.

scholarly journals Adjustment of K' to varying pH and pMg for the creatine kinase, adenylate kinase and ATP hydrolysis equilibria permitting quantitative bioenergetic assessment.

1995 ◽  
Vol 198 (8) ◽  
pp. 1775-1782 ◽  
Author(s):  
E M Golding ◽  
W E Teague ◽  
G P Dobson
Keyword(s):  
Creatine Kinase ◽  
Gibbs Energy ◽  
Adenylate Kinase ◽  
Atp Hydrolysis ◽  
Equilibrium Constants ◽  
Binding Constants ◽  
Acid Dissociation ◽  
Free Magnesium ◽  
Apparent Equilibrium ◽  
Energy Of Formation

Physiologists and biochemists frequently ignore the importance of adjusting equilibrium constants to the ionic conditions of the cell prior to calculating a number of bioenergetic and kinetic parameters. The present study examines the effect of pH and free magnesium levels (free [Mg2+]) on the apparent equilibrium constants (K') of creatine kinase (ATP: creatine N-phosphotransferase; EC 2.7.3.2), adenylate kinase (ATP:AMP phosphotransferase; EC 2.7.4.3) and adenosinetriphosphatase (ATP phosphohydrolase; EC 3.6.1.3) reactions. We show how K' can be calculated using the equilibrium constant of a specified chemical reaction (Kref) and the appropriate acid-dissociation and Mg(2+)-binding constants at an ionic strength (I) of 0.25 mol l-1 and 38 degrees C. Substituting the experimentally determined intracellular pH and free [Mg2+] into the equation containing a known Kref and two variables, pH and free [Mg2+], enables K' to be calculated at the experimental ionic conditions. Knowledge of K' permits calculation of cytosolic phosphorylation ratio ([ATP]/[ADP][Pi]), cytosolic free [ADP], free [AMP], standard transformed Gibbs energy of formation (delta fG' degrees ATP) and the transformed Gibbs energy of the system (delta fG' ATP) for the biological system. Such information is vital for the quantification of organ and tissue bioenergetics under physiological and pathophysiological conditions.

P1, P5-Bis-(5′-adenosyl)pentaphosphate: Is this Adenylate Kinase Inhibitor Substrate for Mitochondrial Processes?

1977 ◽  
Vol 32 (9-10) ◽  
pp. 786-791 ◽  
Author(s):  
Josef Köhrle ◽  
Joachim Lüstorff ◽  
Eckhard Schlimme
Keyword(s):  
Adenylate Kinase ◽  
Kinase Inhibitor ◽  
Adenine Nucleotide ◽  
Nucleoside Diphosphate Kinase ◽  
Liver Mitochondria ◽  
Inhibitory Effect ◽  
Rat Liver Mitochondria ◽  
Intermembrane Space ◽  
Rabbit Muscle ◽  
Inner Mitochondrial Membrane

Abstract 1. P1, P5-Bis-(5′-adenosyl)pentaphosphate (Ap5A) inhibits “soluble” adenylate kinase even when this enzyme is an integral part of the complete mitochondrion. The Ki is 10-5м , i. e. about two orders of magnitude higher than the inhibitor constants determined for the purified adenylate kinase of rabbit muscle and an enzyme preparation separated from the mitochondrial intermembrane space. The weaker inhibitory effect is due to a lower accessibility of the enzyme.2. As to be expected Ap5A which is of the “multisubstrate analogue”-type does not affect mito­ chondrial nucleoside diphosphate kinase.3. Though Ap5A owns the structural elements of both ATP and ADP it is not a substrate of the adenine nucleotide carrier, i.e. neither it is exchanged across the inner mitochondrial membrane nor specifically bound.4. Ap5A is not metabolized by rat liver mitochondria.

Immunochemical approach to the question of inactive subunits in cases of lactate dehydrogenase B subunit deficiency.

1986 ◽  
Vol 32 (1) ◽  
pp. 116-119 ◽  
Author(s):  
M Maekawa ◽  
K Sudo ◽  
T Kanno
Keyword(s):  
Lactate Dehydrogenase ◽  
Equilibrium Constant ◽  
Competitive Reaction ◽  
Apparent Equilibrium Constant ◽  
B Subunit ◽  
B Subunits ◽  
Free Antigen ◽  
Apparent Equilibrium ◽  
Normal Controls

Abstract If there were enzymatically inactive B subunits in a solution containing lactate dehydrogenase (LD) B4 prepared from the hemolysates of heterozygous individuals with LD-B subunit deficiency, the inactive subunits would compete with normal subunits for antibodies to the B4 subunit. Using the activity of normal LD-B4 as an index, we could ascertain the proportion of free antigen (LD-B4) and antibody-antigen complexes (LD-B4-anti-LD-B4) and calculate the apparent equilibrium constant, Keq. Doing so, we found the value for Keq in LD-B subunit deficiency to be smaller than that for normal controls. Evidently the expected competitive reaction takes place. We conclude that heterozygous individuals with LD-B subunit deficiency do indeed produce variant (enzymatically inactive) B subunits of LD.

Adenylate Kinase from Maize Leaves: True Substrates, Inhibition by P1 , P5-di(adenosine-5′) pentaphosphate and Kinetic Mechanism

1990 ◽  
Vol 45 (6) ◽  
pp. 607-613 ◽  
Author(s):  
Leszek A. Kleczkowski ◽  
Douglas D. Randall ◽  
Warren L. Zahler
Keyword(s):  
Adenylate Kinase ◽  
Kinetic Studies ◽  
Kinetic Mechanism ◽  
Reverse Reaction ◽  
Plant Tissues ◽  
Forward Reaction ◽  
Higher Plant ◽  
Maize Leaves ◽  
Variable Substrate ◽  
Free Magnesium

Abstract Purified maize leaf adenylate kinase (AK) was shown to use one molecule each of free ADP and Mg-ADP as well as free AM P and Mg-ATP as substrates in the forward and reverse reaction, respectively. This was deduced from substrate kinetic studies which were carried out under conditions of strictly defined concentrations of free and Mg-complexed adenylate species and under controlled free magnesium levels. Apparent Km values of the substrates of AK were 3 and 6 μM for ADP and Mg-ADP, respectively (forward reaction), and 69 and 25 μM for free AMP and Mg-ATP, respectively (reverse reaction). The enzyme was competitively inhibited by P1,P5-di(adenosine-5′)pentaphosphate (Ap5A), a bisubstrate analog of AK reaction, with apparent Ki values in the range of 11 -80 nM , depending on variable substrate. Substrate kinetic studies and inhibition patterns with Ap5A suggested a sequential random kinetic mechanism in both directions of the reaction. These properties of a higher plant AK are similar or analogous to those previously established for the enzyme from yeast and non-plant tissues.

The activities of nucleoside diphosphate kinase and adenylate kinase are influenced by their interaction

Plant Science ◽  
2008 ◽  
Vol 174 (2) ◽  
pp. 192-199 ◽  
Author(s):  
Monika Johansson ◽  
Jenni Hammargren ◽  
Eva Uppsäll ◽  
Alasdair MacKenzie ◽  
Carina Knorpp
Keyword(s):  
Adenylate Kinase ◽  
Nucleoside Diphosphate Kinase

scholarly journals Stimulation of phospholipase D in rabbit platelet membranes by nucleoside triphosphates and by phosphocreatine: roles of membrane-bound GDP, nucleoside diphosphate kinase and creatine kinase

1994 ◽  
Vol 299 (3) ◽  
pp. 701-709 ◽  
Author(s):  
X T Fan ◽  
J L Sherwood ◽  
R J Haslam
Keyword(s):  
Creatine Kinase ◽  
Phospholipase D ◽  
Phorbol Esters ◽  
Nucleoside Diphosphate Kinase ◽  
Rabbit Platelet ◽  
Platelet Membranes ◽  
Nucleoside Triphosphates ◽  
Membrane Bound ◽  
Fold Stimulation ◽  
Stimulation Of

Previous work has shown that guanosine 5′-[gamma-thio]triphosphate (GTP[S]) and GTP stimulate phospholipase D (PLD) in rabbit platelet membranes and that these effects are greatly enhanced by pretreatment of platelets with phorbol esters that activate protein kinase C [Van der Meulen and Haslam (1990), Biochem. J. 271, 693-700]. In the present study, the effects of Mg2+, various nucleoside triphosphates and phosphocreatine (PCr) were investigated. Platelet membranes containing phospholipids labelled with [3H]glycerol were assayed for PLD in the presence of an optimal Mg2+ concentration (10 mM) by measuring [3H]phosphatidylethanol formation in incubations that included 300 mM ethanol. In membranes from phorbolester-treated platelets, the same maximal increases in PLD activity (5-fold) were seen with 1 microM GTP[S]), and 100 microM GTP. Addition of adenosine 5′-[gamma-thio]triphosphate (ATP[S]), ITP, XTP, UTP and CTP had similar stimulatory effects, but only at > or = 1 mM. In contrast, ATP had a biphasic action, causing a maximal (2-fold) stimulation at 10 microM and smaller effects at higher concentrations; the inhibitory component of the action of ATP was blocked by 2 microM staurosporine. Guanosine 5′-[beta-thio]diphosphate decreased the stimulatory effects of ATP and ATP[S]. UDP, which can inhibit nucleoside diphosphate kinase (NDPK), decreased the activation of PLD by ATP[S], ATP, XTP, CTP and to a lesser extent ITP, but had no effect on the actions of GTP[S] and GTP. Rabbit platelet membranes contained NDPK and addition of [gamma-32P]ATP led to the formation of [32P]GTP in amounts sufficient to explain most or all of the activation of PLD; UDP prevented GTP formation. PCr (0.04-1 mM) also stimulated membrane PLD activity, an effect that was dependent on endogenous membrane-bound creatine kinase (CK). UDP and guanosine 5′-[beta-thio]diphosphate each inhibited this effect of PCr. The results show that in rabbit platelet membranes, CK, NDPK and the GTP-binding protein that activates PLD can be functionally coupled. However, assay of membrane preparations at increasing dilutions showed that stimulation of PLD by the compounds studied, with the partial exception of ATP[S], involved diffusible rather than protein-bound intermediates.

scholarly journals Phloem Loading of Sorbitol in Apple (Malus domestica Borkh.): Cloning and Sequence Analysis of Potential H+/Sorbitol Symporters from a Mature Leaf cDNA Library

HortScience ◽  
2004 ◽  
Vol 39 (4) ◽  
pp. 756B-756
Author(s):  
Edwin J. Reidel* ◽  
Brian G. Ayre ◽  
E. Robert Turgeon ◽  
Lailiang Cheng
Keyword(s):  
Cdna Library ◽  
Malus Domestica ◽  
Phloem Loading ◽  
Open Reading Frames ◽  
Sugar Transporter ◽  
Sugar Transporters ◽  
Apple Leaves ◽  
Complete Sequencing ◽  
Membrane Bound ◽  
Reading Frames

Sorbitol (d-glucitol) is the major end product of photosynthesis in apple (Malus domestica Borkh.), as well as the predominant phloem-translocated carbohydrate. The mechanism by which sorbitol is phloem-loaded for transport to heterotrophic sink tissues is unknown. We hypothesized that a plasma membrane-bound H+/sorbitol symporter mediates apoplastic phloem-loading of sorbitol. To discover genes potentially encoding sorbitol transporters, a cDNA library was constructed from mature `Gala' apple leaves. A homologous probe was synthesized via PCR with primers were designed against the cherry fruit sorbitol transporter, PcSot1, and using library lysate as template. From an initial plating of approximately 5 × 105 clones, twelve positives were identified after three rounds of hybridization screening. Following single-pass, 5' end sequencing, the clones were sorted into four contiguous sequences. One clone was chosen from each contig for complete sequencing. The four clones, provisionally named MdSOT1-4 (Malus domesitca Sorbitol Transporter), potentially encode full-length cDNAs for sorbitol transporters: Translated-BLAST searching (blastx) revealed that the open reading frames encode the complete Pfam sugar transporter domain, and the most significant alignments are with sequences encoding known- and putative polyol and sugar transporters.

scholarly journals The Oxidoreductase DsbA1 negatively influences 2,4-diacetylphloroglucinol biosynthesis by interfering the function of Gcd in Pseudomonas fluorescens 2P24

2020 ◽  
Author(s):  
Bo Zhang ◽  
Hui Zhao ◽  
Xiaogang Wu ◽  
Li-Qun Zhang
Keyword(s):  
Pseudomonas Fluorescens ◽  
Glucose Dehydrogenase ◽  
Fine Tuning ◽  
Two Component System ◽  
Independent Manner ◽  
Disulfide Oxidoreductase ◽  
Two Component ◽  
Biocontrol Activity ◽  
Membrane Bound

Abstract The polyketide antibiotic 2,4-diacetylphloroglucinol (2,4-DAPG), produced by Pseudomonas fluorescens 2P24, is positively regulated by the GacS-GacA two-component system. Here we reported on the characterization of DsbA1 (disulfide oxidoreductase) as novel regulator of biocontrol activity in P. fluorescens . Our data showed that mutation of dsbA1 caused the accumulation of 2,4-DAPG in a GacA-independent manner. Further analysis indicated that DsbA1 interacts with membrane-bound glucose dehydrogenase Gcd, which positively regulates the production of 2,4-DAPG. Mutation of cysteine (C)-235, C275, and C578 of Gcd, significantly reduced the interaction with DsbA1, enhanced the activity of Gcd and increased 2,4-DAPG production. Taken together, our results suggest that DsbA1 regulates the 2,4-DAPG concentration via fine-tuning the function of Gcd in P. fluorescens 2P24.

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