Polyphosphate kinase
Encyclopedia
In enzymology, a polyphosphate kinase is an enzyme
that catalyzes
the formation of polyphosphate from ATP, with chain lengths of up to a thousand or more orthophosphate molecules.
Thus, the two substrates
of this enzyme are ATP
and (phosphate)n, whereas its two products
are ADP
and (phosphate)n+1.
It is a membrane protein
and goes through an intermediate stage during the reaction where it is autophosphorylated with a phosphate group covalently linked to a basic amino acid residue through an N-P bond.
This enzyme belongs to the family of transferase
s, specifically those transferring phosphorus-containing groups (phosphotransferase
s) with a phosphate group as acceptor. The systematic name of this enzyme class is ATP:polyphosphate phosphotransferase. This enzyme is also called polyphosphoric acid kinase. This enzyme participates in oxidative phosphorylation
.
have been solved for this class of enzymes, with PDB
accession codes , , and .
Enzyme
Enzymes are proteins that catalyze chemical reactions. In enzymatic reactions, the molecules at the beginning of the process, called substrates, are converted into different molecules, called products. Almost all chemical reactions in a biological cell need enzymes in order to occur at rates...
that catalyzes
Catalysis
Catalysis is the change in rate of a chemical reaction due to the participation of a substance called a catalyst. Unlike other reagents that participate in the chemical reaction, a catalyst is not consumed by the reaction itself. A catalyst may participate in multiple chemical transformations....
the formation of polyphosphate from ATP, with chain lengths of up to a thousand or more orthophosphate molecules.
- ATP + (phosphate)n
ADP + (phosphate)n+1
Thus, the two substrates
Substrate (biochemistry)
In biochemistry, a substrate is a molecule upon which an enzyme acts. Enzymes catalyze chemical reactions involving the substrate. In the case of a single substrate, the substrate binds with the enzyme active site, and an enzyme-substrate complex is formed. The substrate is transformed into one or...
of this enzyme are ATP
Adenosine triphosphate
Adenosine-5'-triphosphate is a multifunctional nucleoside triphosphate used in cells as a coenzyme. It is often called the "molecular unit of currency" of intracellular energy transfer. ATP transports chemical energy within cells for metabolism...
and (phosphate)n, whereas its two products
Product (chemistry)
Product are formed during chemical reactions as reagents are consumed. Products have lower energy than the reagents and are produced during the reaction according to the second law of thermodynamics. The released energy comes from changes in chemical bonds between atoms in reagent molecules and...
are ADP
Adenosine diphosphate
Adenosine diphosphate, abbreviated ADP, is a nucleoside diphosphate. It is an ester of pyrophosphoric acid with the nucleoside adenosine. ADP consists of the pyrophosphate group, the pentose sugar ribose, and the nucleobase adenine....
and (phosphate)n+1.
It is a membrane protein
Membrane protein
A membrane protein is a protein molecule that is attached to, or associated with the membrane of a cell or an organelle. More than half of all proteins interact with membranes.-Function:...
and goes through an intermediate stage during the reaction where it is autophosphorylated with a phosphate group covalently linked to a basic amino acid residue through an N-P bond.
This enzyme belongs to the family of transferase
Transferase
In biochemistry, a transferase is an enzyme that catalyzes the transfer of a functional group from one molecule to another . For example, an enzyme that catalyzed this reaction would be a transferase:In this example, A would be the donor, and B would be the acceptor...
s, specifically those transferring phosphorus-containing groups (phosphotransferase
Phosphotransferase
Phosphotransferases are a category of enzymes that catalyze phosphorylation reactions. The general form of the reactions they catalyze is: A—P + B ⇔ B—P + A...
s) with a phosphate group as acceptor. The systematic name of this enzyme class is ATP:polyphosphate phosphotransferase. This enzyme is also called polyphosphoric acid kinase. This enzyme participates in oxidative phosphorylation
Oxidative phosphorylation
Oxidative phosphorylation is a metabolic pathway that uses energy released by the oxidation of nutrients to produce adenosine triphosphate . Although the many forms of life on earth use a range of different nutrients, almost all aerobic organisms carry out oxidative phosphorylation to produce ATP,...
.
Structural studies
As of late 2007, 3 structuresTertiary structure
In biochemistry and molecular biology, the tertiary structure of a protein or any other macromolecule is its three-dimensional structure, as defined by the atomic coordinates.-Relationship to primary structure:...
have been solved for this class of enzymes, with PDB
Protein Data Bank
The Protein Data Bank is a repository for the 3-D structural data of large biological molecules, such as proteins and nucleic acids....
accession codes , , and .