|MadSci Network: Biochemistry|
Apyrase enzymes convert nucleotide triphosphates into nucleotide monophosphates and phosphate. Here is an example of an apyrase reaction with Adenosine tri-phosphate (ATP).
ATP + 2H20 -----> AMP + 2 PhosphateShi et. al. provide an excellent summary of the cellular localization of apyrase in: J. Biol. Chem., Vol. 276, Issue 20, 17474- 17478, May 18, 2001, Molecular cloning and Characterization of a Novel Mammalian Endo-apyrase, Shi JD, Kukar T, Wang CY, Li QZ, Cruz PE, Davoodi-Semiromi A, Yang P, Gu Y, Lian W, Wu DH, She JX. An excerpt from this paper explaining the cellular localization of apyrase is below, and you can read the entire paper by following this link.
There are two types of apyrases, ecto and endo pyrase (2). Ecto-apyrases
are apyrase enzymes with their catalytic domain exposed on the cell
surface (1-3). and are believed to be involved in many processes such as
neurotransmission (4), platelet aggregation, and blood pressure
regulation (5). On the other hand, endo-apyrases such as uridine
diphosphatase and the 700-kDa lysosomal apyrase-like protein (LALP70) are
apyrase enzymes with their catalytic domain localized intracellularly (6,
7). The biological functions of the endo-apyrases are unknown, although
it was suggested that they are important for regulating the level of
activated sugar during protein glycosylation.
Recently, Wang and Guidotti (6) identified the first mammalian endo-
apyrase, human uridine diphosphatase. This enzyme is predicted to be a
610-amino acid protein with two putative transmembrane domains. Using a
myc-tagged version of this protein, this enzyme was found to be in the
luminal side of the Golgi apparatus.
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