Adenosine 5'-Triphosphatase
Official Full Name
Adenosine 5'-Triphosphatase
Background
ATPases are a class of enzymes that catalyze the decomposition of ATP into ADP and a free phosphate ion. This dephosphorylation reaction releases energy, which the enzyme (in most cases) harnesses to drive other chemical reactions that would not otherwise occur. This process is widely used in all known forms of life. Some such enzymes are integral membrane proteins (anchored within biological membranes), and move solutes across the membrane, typically against their concentRation gradient. These are called transmembrane ATPases.
Synonyms
ATP phosphohydrolase; ATPase; Adenosine 5'-Triphosphatase; EC 3.6.1.3; adenylpyrophosphatase; ATP monophosphatase; triphosphatase; SV40 T-antigen; adenosine 5'-triphosphatase; ATP hydrolase# complex V (mitochondrial electron transport); (Ca2+ + Mg2+)-ATPase; HCO3−-ATPase; adenosine triphosphatase
Introductions
Adenosine 5'-triphosphatase, adenosine pyrophosphatase, ATP monophosphatase, triphosphatase, are a class of enzymes or inverse reactions that catalyze the breakdown of ATP to ADP and free phosphate ions. This dephosphorylation reaction releases energy, which the enzyme (in most cases) uses to drive other chemical reactions that would not otherwise occur. This process is widely used in all known forms of life. Some such enzymes are integral membrane proteins (anchored within biological membranes) and move solutes across the membrane, usually against their concentration gradient. These are called transmembrane ATPases.
Biochemical/physiological effects
Adenosine 5'-triphosphatase hydrolyzes ATP to ADP and orthophosphate. The hydrolysis process is accompanied by the exchange of sodium and potassium ions across the plasma membrane. This enzyme is present in almost all tissues of higher organisms, but is most abundant in the kidney because it reabsorbs sodium ions from the glomerular filtrate. Na/K-ATPase is affected by intracellular calcium ion changes. It is also sensitive and is inhibited by vanadate and (in vitro) SPAI-1 (a peptide isolated from porcine duodenum). Adenosine 5'-triphosphatase has been shown to be regulated by phosphorylation of protein kinase A (PKA). This membrane enzyme hydrolyzes ATP to ADP and orthophosphate. The hydrolysis process is accompanied by the exchange of sodium and potassium ions across the plasma membrane. This enzyme is present in almost all tissues of higher organisms, but is most abundant in the kidney because it reabsorbs sodium ions from the glomerular filtrate. Na/K-ATPase is affected by intracellular calcium ion changes. It has been shown to be regulated by phosphorylation of protein kinase A (PKA).
Functions
Adenosine 5'-triphosphatase imports many substances into the cell that are required for metabolism and exports toxicants, metabolic wastes, and other substances that may impede cellular processes. For example, sodium-potassium ATPase (also known as sodium/potassium ion ATPase) regulates the intracellular sodium/potassium ion concentration, thus maintaining the resting potential of the cell, and hydrogen-potassium ATPase (also known as hydrogen/potassium ion ATPase or gastric proton pump) maintains an acidified environment in the stomach. Some adenosine 5'-triphosphatases can cause charge flow inside and outside the membrane, while others cannot, so these transport proteins can be classified as electrogenic and non-electrogenic.
Reaction mechanism
Adenosine 5'-triphosphatase coupled to ATP hydrolysis is a strictly chemical reaction, i.e., each molecule of ATP hydrolysis enables a certain number of solution molecules to be transported. For Na/K-ATPase, each molecule of ATP hydrolysis enables 3 sodium ions to be transported out of the cell, while 2 potassium ions are transported in. Transmembrane adenosine 5'-triphosphatases require the energy generated by ATP hydrolysis because these enzymes need to do work: they transport substances against the direction in which they are thermodynamically more likely to occur, in other words, using the membrane as a reference, they can transport substances from one side of a low concentration to the other side of a high concentration.
Applications
ATPase is used for the release of inorganic phosphorus from ATP. ATPase from porcine cerebral cortex has been used for the inhibition assay of Na/K-ATPase activity.
