adenosine triphosphatase

adenosine tri·phos·pha·tase (tr-fsf-ts, -tz)

n.

ATPase.

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adenosine triphosphatase (ATPase),

an enzyme in skeletal muscle and other tissues that catalyzes the hydrolysis of adenosine triphosphate to adenosine diphosphate and inorganic phosphate. Among various enzymes in this group, mitochondrial ATPase is involved in obtaining energy for cellular metabolism, and myosin ATPase is involved in muscle contraction.

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adenosine

one of the four bases that make up RNA and DNA containing the pentose sugar, 2-deoxy-d-ribose. Adenosine nucleotides are involved in the energy metabolism of all cells. Adenosine can be linked to a chain of one, two or three phosphate groups to form adenosine monophosphate (AMP), adenosine diphosphate (ADP) or adenosine triphosphate (ATP). The bond between the phosphate groups in ADP or the two bonds between the phosphate groups in ATP are called high-energy bonds because hydrolysis of a high-energy bond provides a large amount of free energy that can be used to drive other processes that would not otherwise occur spontaneously. The energy that is derived from the oxidation of carbohydrates, fats or proteins is used to synthesize ATP. The energy stored in ATP is then used directly or indirectly to drive all other cellular processes that require energy, of which there are four major types: (1) the transport of molecules and ions across cell membranes against concentration gradients, which maintains the internal environment of the cell and produces the membrane potential for the conduction of nerve impulses; (2) the contraction of muscle fibers and other fibers producing the motion of cells; (3) the synthesis of chemical compounds; (4) the synthesis of other high-energy compounds.

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cyclic adenosine monophosphate (cyclic AMP, cAMP, 3′,5′-cAMP)

a cyclic nucleotide, adenosine 3′,5′-cyclic monophosphate, involved in the action of many hormones, including catecholamines, ACTH and vasopressin. The hormone (first message) binds to a specific β-receptor on the cell membrane of target cells. This activates an enzyme, adenylate cyclase, which produces cyclic AMP from ATP. Cyclic AMP acts as a second messenger activating other enzymes via covalent modulation within the cell.

adenosine deaminase

key enzyme in degradation pathway of adenosine; catalyzes the deamination of adenosine to inosine. Many cases of severe combined immunodeficiency syndrome in humans result from a heritable lack of adenosine deaminase.

adenosine diphosphate (ADP)

a nucleotide, adenosine 5′-pyrophosphate, produced by the hydrolysis of adenosine triphosphate (ATP). It is then converted back to ATP by oxidative, substrate or photosynthic phosphorylation. See also adp.

adenosine monophosphate (AMP)

a nucleotide, adenosine 5′-phosphate, involved in energy metabolism and nucleotide synthesis. Called also adenylic acid.

adenosine triphosphatase

a term used to refer to the enzymatic activity of certain intercellular processes that split ATP to form ADP and inorganic phosphate, when the energy released is not used for the synthesis of chemical compounds. Examples are the splitting of ATP in muscle contraction in myosin head-groups and the transport of ions across cell membranes. Called also ATPase.

adenosine triphosphatase test

used as a quantitative assay of the amount of avian leukosis virus in chicken tissues or tissue cultures. It depends on the virus's characteristic of carrying on its surface a phosphatase enzyme that dephosphorylates adenosine triphosphate.

adenosine triphosphate (ATP)

a nucleotide, adenosine 5′-triphosphate, occurring in all cells, where it stores energy in the form of high-energy phosphate bonds. Free energy of hydrolysis is supplied to drive metabolic reactions or to transport molecules against concentration gradients, when ATP is hydrolyzed to ADP and inorganic phosphate or to AMP and inorganic pyrophosphate. ATP is also used to produce high-energy phosphorylated intermediary metabolites, such as glucose-6-phosphate.