MadSci Network: Biochemistry

Re: what is the mechanism of action &cellular localization of apyrase????

Date: Mon Apr 25 11:38:39 2005
Posted By: Will Rosner, Staff, Epidemiology, Alberta Cancer Board
Area of science: Biochemistry
ID: 1109596169.Bc

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 Phosphate
Shi 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.

1. Plesner, L. (1995) Int. Rev. Cytol. 158, 141-214
2. Komoszynski, M., and Wojtczak, A. (1996) Biochim. Biophys. Acta 1310, 233-241
3. Kaczmarek, E., Koziak, K., Sevigny, J., Siegel, J. B., Anrather, J., Beaudoin, A. R, Bach, F. H., and Robson, S. C. (1996) J. Biol. Chem. 271, 33116-33122
4. Marcus, A. J., Broekman, M. J., Drosopoulos, J. H. G., Islam, N., Alyonycheva, T. N., Safier, L. B., Hajiar, K. A., Posnett, D. N., Schoenborn, M. A., Schooley, R. B., Gayle, R. B., and Maliszewski, C. R. (1997) J. Clin. Invest. 99, 1351-1360
5. Zimmermann, H. (1996) Biochem. J. 285, 345-365
6. Wang, T. F., and Guidotti, G. (1998) J. Biol. Chem. 273, 11392- 11399

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