Apyrase (, ''ATP-diphosphatase'',

adenosine Adenosine (symbol A) is an organic compound that occurs widely in nature in the form of diverse derivatives. The molecule consists of an adenine attached to a ribose via a β-N9- glycosidic bond. Adenosine is one of the four nucleoside build ...

diphosphatase, ''ADPase'', ''ATP diphosphohydrolase'') is a

calcium Calcium is a chemical element; it has symbol Ca and atomic number 20. As an alkaline earth metal, calcium is a reactive metal that forms a dark oxide-nitride layer when exposed to air. Its physical and chemical properties are most similar to it ...

-activated plasma membrane-bound

enzyme An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...

(magnesium can also activate it) () that catalyses the

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

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 (approx 10) and another with no selectivity (ratio 1). It can also act on ADP and other nucleoside triphosphates and diphosphates with the general reaction being NTP -> NDP + Pi -> NMP + 2Pi. This is the same activity that has been employed in the degradation of unincorporated nucleosides during

pyrosequencing Pyrosequencing is a method of DNA sequencing (determining the order of nucleotides in DNA) based on the "sequencing by synthesis" principle, in which the sequencing is performed by detecting the nucleotide incorporated by a DNA polymerase. Pyrosequ ...

. The salivary apyrases of blood-feeding

arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...

s are

nucleotide Nucleotides are Organic compound, 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 o ...

hydrolysing

s that are implicated in the inhibition of host

platelet aggregation Platelets or thrombocytes () are a part of blood whose function (along with the coagulation factors) is to react to bleeding from blood vessel injury by clumping to form a blood clot. Platelets have no cell nucleus; they are fragments of cytop ...

through the

extracellular This glossary of biology terms is a list of definitions of fundamental terms and concepts used in biology, the study of life and of living organisms. It is intended as introductory material for novices; for more specific and technical definitions ...

adenosine diphosphate 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 backbon ...

References

External links

* Protein families EC 3.6.1 {{3.6-enzyme-stub