High-energy phosphate

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High-energy phosphate can mean one of two things:

High-energy phosphate bonds are usually pyrophosphate bonds, acid anhydride linkages formed by taking phosphoric acid derivatives and dehydrating them. As a consequence, the hydrolysis of these bonds is exergonic under physiological conditions, releasing Gibbs free energy.

"High energy" phosphate reactions
Reaction
ATP + H2O → ADP + Pi
ADP + H2O → AMP + Pi
ATP + H2O → AMP + PPi
PPi + H2O → 2 Pi

Except for PPi → 2 Pi, these reactions are, in general, not allowed to go uncontrolled in the human cell but are instead coupled to other processes needing energy to drive them to completion. Thus, high-energy phosphate reactions can:

The one exception is of value because it allows a single hydrolysis, ATP + H2O → AMP + PPi, to effectively supply the energy of hydrolysis of two high-energy bonds, with the hydrolysis of PPi being allowed to go to completion in a separate reaction. The AMP is regenerated to ATP in two steps, with the equilibrium reaction ATP + AMP ↔ 2ADP, followed by regeneration of ATP by the usual means, oxidative phosphorylation or other energy-producing pathways such as glycolysis.

Often, high-energy phosphate bonds are denoted by the character '~'. In this "squiggle" notation, ATP becomes A-P~P~P. The squiggle notation was invented by Fritz Albert Lipmann, who first proposed ATP as the main energy transfer molecule of the cell, in 1941. [4] Lipmann's notation emphasizes the special nature of these bonds. [5] Stryer states:

ATP is often called a high energy compound and its phosphoanhydride bonds are referred to as high-energy bonds. There is nothing special about the bonds themselves. They are high-energy bonds in the sense that free energy is released when they are hydrolyzed, for the reasons given above. Lipmann’s term "high-energy bond" and his symbol ~P (squiggle P) for a compound having a high phosphate group transfer potential are vivid, concise, and useful notations. In fact Lipmann's squiggle did much to stimulate interest in bioenergetics. [5]

The term 'high energy' with respect to these bonds can be misleading because the negative free energy change is not due directly to the breaking of the bonds themselves. The breaking of these bonds, like the breaking of most bonds, is endergonic and consumes energy rather than releasing it. The negative free energy change comes instead from the fact that the bonds formed after hydrolysis - or the phosphorylation of a residue by ATP - are lower in energy than the bonds present before hydrolysis. (This includes all of the bonds involved in the reaction, not just the phosphate bonds themselves). This effect is due to a number of factors including increased resonance stabilization and solvation of the products relative to the reactants, and destabilization of the reactants due to electrostatic repulsion between neighboring phosphorus atoms. [6]

Related Research Articles

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Hydrolysis is any chemical reaction in which a molecule of water breaks one or more chemical bonds. The term is used broadly for substitution, elimination, and solvation reactions in which water is the nucleophile.

<span class="mw-page-title-main">Nucleotide</span> Biological molecules that form the building blocks of nucleic acids

Nucleotides are organic molecules composed of a nitrogenous base, a pentose sugar and a phosphate. They serve as monomeric units of the nucleic acid polymers – deoxyribonucleic acid (DNA) and ribonucleic acid (RNA), both of which are essential biomolecules within all life-forms on Earth. Nucleotides are obtained in the diet and are also synthesized from common nutrients by the liver.

<span class="mw-page-title-main">Adenosine diphosphate</span> Chemical compound

Adenosine diphosphate (ADP), also known as adenosine pyrophosphate (APP), is an important organic compound in metabolism and is essential to the flow of energy in living cells. ADP consists of three important structural components: a sugar backbone attached to adenine and two phosphate groups bonded to the 5 carbon atom of ribose. The diphosphate group of ADP is attached to the 5’ carbon of the sugar backbone, while the adenine attaches to the 1’ carbon.

<span class="mw-page-title-main">Adenosine monophosphate</span> Chemical compound

Adenosine monophosphate (AMP), also known as 5'-adenylic acid, is a nucleotide. AMP consists of a phosphate group, the sugar ribose, and the nucleobase adenine. It is an ester of phosphoric acid and the nucleoside adenosine. As a substituent it takes the form of the prefix adenylyl-.

<span class="mw-page-title-main">Pyrophosphate</span> Class of chemical compounds

In chemistry, pyrophosphates are phosphorus oxyanions that contain two phosphorus atoms in a P−O−P linkage. A number of pyrophosphate salts exist, such as disodium pyrophosphate and tetrasodium pyrophosphate, among others. Often pyrophosphates are called diphosphates. The parent pyrophosphates are derived from partial or complete neutralization of pyrophosphoric acid. The pyrophosphate bond is also sometimes referred to as a phosphoanhydride bond, a naming convention which emphasizes the loss of water that occurs when two phosphates form a new P−O−P bond, and which mirrors the nomenclature for anhydrides of carboxylic acids. Pyrophosphates are found in ATP and other nucleotide triphosphates, which are important in biochemistry. The term pyrophosphate is also the name of esters formed by the condensation of a phosphorylated biological compound with inorganic phosphate, as for dimethylallyl pyrophosphate. This bond is also referred to as a high-energy phosphate bond.

Phosphagens, also known as macroergic compounds, are high energy storage compounds, also known as high-energy phosphate compounds, chiefly found in muscular tissue in animals. They allow a high-energy phosphate pool to be maintained in a concentration range, which, if it all were adenosine triphosphate (ATP), would create problems due to the ATP-consuming reactions in these tissues. As muscle tissues can have sudden demands for much energy, these compounds can maintain a reserve of high-energy phosphates that can be used as needed, to provide the energy that could not be immediately supplied by glycolysis or oxidative phosphorylation. Phosphagens supply immediate but limited energy.

<span class="mw-page-title-main">Guanosine triphosphate</span> Chemical compound

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<span class="mw-page-title-main">Phosphodiester bond</span> –O– linkage between phosphoric acid and two other compounds

In chemistry, a phosphodiester bond occurs when exactly two of the hydroxyl groups in phosphoric acid react with hydroxyl groups on other molecules to form two ester bonds. The "bond" involves this linkage C−O−PO−2O−C. Discussion of phosphodiesters is dominated by their prevalence in DNA and RNA, but phosphodiesters occur in other biomolecules, e.g. acyl carrier proteins, phospholipids and the cyclic forms of GMP and AMP.

A nucleoside triphosphate is a nucleoside containing a nitrogenous base bound to a 5-carbon sugar, with three phosphate groups bound to the sugar. They are the molecular precursors of both DNA and RNA, which are chains of nucleotides made through the processes of DNA replication and transcription. Nucleoside triphosphates also serve as a source of energy for cellular reactions and are involved in signalling pathways.

Bioenergetics is a field in biochemistry and cell biology that concerns energy flow through living systems. This is an active area of biological research that includes the study of the transformation of energy in living organisms and the study of thousands of different cellular processes such as cellular respiration and the many other metabolic and enzymatic processes that lead to production and utilization of energy in forms such as adenosine triphosphate (ATP) molecules. That is, the goal of bioenergetics is to describe how living organisms acquire and transform energy in order to perform biological work. The study of metabolic pathways is thus essential to bioenergetics.

<span class="mw-page-title-main">Adenylate kinase</span> Class of enzymes

Adenylate kinase is a phosphotransferase enzyme that catalyzes the interconversion of the various adenosine phosphates. By constantly monitoring phosphate nucleotide levels inside the cell, ADK plays an important role in cellular energy homeostasis.

<span class="mw-page-title-main">ATP hydrolysis</span> Catabolism of ATP into ADP

ATP hydrolysis is the catabolic reaction process by which chemical energy that has been stored in the high-energy phosphoanhydride bonds in adenosine triphosphate (ATP) is released after splitting these bonds, for example in muscles, by producing work in the form of mechanical energy. The product is adenosine diphosphate (ADP) and an inorganic phosphate (Pi). ADP can be further hydrolyzed to give energy, adenosine monophosphate (AMP), and another inorganic phosphate (Pi). ATP hydrolysis is the final link between the energy derived from food or sunlight and useful work such as muscle contraction, the establishment of electrochemical gradients across membranes, and biosynthetic processes necessary to maintain life.

<span class="mw-page-title-main">Phosphoric acids and phosphates</span> Class of chemical species; phosphorus oxoacids and their deprotonated derivatives

In chemistry, a phosphoric acid, in the general sense, is a phosphorus oxoacid in which each phosphorus (P) atom is in the oxidation state +5, and is bonded to four oxygen (O) atoms, one of them through a double bond, arranged as the corners of a tetrahedron. Two or more of these PO4 tetrahedra may be connected by shared single-bonded oxygens, forming linear or branched chains, cycles, or more complex structures. The single-bonded oxygen atoms that are not shared are completed with acidic hydrogen atoms. The general formula of a phosphoric acid is Hn+2−2xPnO3n+1−x, where n is the number of phosphorus atoms and x is the number of fundamental cycles in the molecule's structure, between 0 and n + 2/2.

<span class="mw-page-title-main">Nucleoside-diphosphate kinase</span> Class of enzymes

Nucleoside-diphosphate kinases are enzymes that catalyze the exchange of terminal phosphate between different nucleoside diphosphates (NDP) and triphosphates (NTP) in a reversible manner to produce nucleotide triphosphates. Many NDP serve as acceptor while NTP are donors of phosphate group. The general reaction via ping-pong mechanism is as follows: XDP + YTP ←→ XTP + YDP. NDPK activities maintain an equilibrium between the concentrations of different nucleoside triphosphates such as, for example, when guanosine triphosphate (GTP) produced in the citric acid (Krebs) cycle is converted to adenosine triphosphate (ATP). Other activities include cell proliferation, differentiation and development, signal transduction, G protein-coupled receptor, endocytosis, and gene expression.

<span class="mw-page-title-main">Apyrase</span> Enzyme

Apyrase is a calcium-activated plasma membrane-bound enzyme that catalyses the hydrolysis of ATP to yield AMP and inorganic phosphate. Two isoenzymes are found in commercial preparations from S. tuberosum. One with a higher ratio of substrate selectivity for ATP:ADP and another with no selectivity.

<span class="mw-page-title-main">Phosphoenolpyruvic acid</span> Chemical compound

Phosphoenolpyruvate is the carboxylic acid derived from the enol of pyruvate and phosphate. It exists as an anion. PEP is an important intermediate in biochemistry. It has the highest-energy phosphate bond found in organisms, and is involved in glycolysis and gluconeogenesis. In plants, it is also involved in the biosynthesis of various aromatic compounds, and in carbon fixation; in bacteria, it is also used as the source of energy for the phosphotransferase system.

<span class="mw-page-title-main">Deoxycytidine triphosphate</span> Chemical compound

Deoxycytidine triphosphate (dCTP) is a nucleoside triphosphate that contains the pyrimidine base cytosine. The triphosphate group contains high-energy phosphoanhydride bonds, which liberate energy when hydrolized.

<span class="mw-page-title-main">Nucleic acid metabolism</span> Process

Nucleic acid metabolism is a collective term that refers to the variety of chemical reactions by which nucleic acids are either synthesized or degraded. Nucleic acids are polymers made up of a variety of monomers called nucleotides. Nucleotide synthesis is an anabolic mechanism generally involving the chemical reaction of phosphate, pentose sugar, and a nitrogenous base. Degradation of nucleic acids is a catabolic reaction and the resulting parts of the nucleotides or nucleobases can be salvaged to recreate new nucleotides. Both synthesis and degradation reactions require multiple enzymes to facilitate the event. Defects or deficiencies in these enzymes can lead to a variety of diseases.

In enzymology, an ATP diphosphatase (EC 3.6.1.8) is an enzyme that catalyzes the chemical reaction

References

  1. "ATP | Learn Science at Scitable". www.nature.com. Retrieved 2021-04-12.
  2. "ATP/ADP". Chemistry LibreTexts. 2013-10-02. Retrieved 2021-04-12.
  3. "Important High Energy Molecules in Metabolism". Chemistry LibreTexts. 2013-10-02. Retrieved 2021-04-12.
  4. Lipmann F (1941). "Metabolic generation and utilization of phosphate bond energy". Adv. Enzymol. 1: 99–162. ISSN   0196-7398.
  5. 1 2 Lubert Stryer Biochemistry, 3rd edition, 1988. Chapter 13, p. 318
  6. Garrett, Reginald H.; Grisham, Charles M. (2016). Biochemistry (6th ed.). Cengage Learning. p. 64. ISBN   978-1305577206.

Further reading