Extracellular phosphatase

F. Asmar, T. S. Gahoonia, and N. E. Nielsen, Barley genotypes differ in activity of soluble extracellular phosphatase and depletion of organic phosphorus in the rhizo.sphere soil. Plant Soil 172 1 (1995). 

E. J. Joner and 1. Jakobsen, Growth and extracellular phosphatase activity of arbus-cular mycorrhizal hyphae as influenced by soil organic matter. Soil Biol. Bioehem. 27 1153 (1995). 

Utilization of phosphate monoesters by microalgae and bacteria is effected by phosphomonoesterases (phosphatases) of broad specificity present at the cell surface. Hydrolytic release of PO4- from sugar phosphates, nucleotide phosphates, phospholipids, and phenyl phosphates, to name a few, enables a wide variety of phosphorus containing compounds to be utilized as phosphorus sources for growth of microbes. Ultrastructural observations and results from biochemical experiments indicate that extracellular phosphatases cleave the phosphate moiety from dissolved organic phosphorus compounds, which is then internalized, leaving the carbon skeleton outside the cell (Kuenzler and Perras, 1965 Doonan and Jensen, 1977). 

Extracellular phosphatase activity has been detected in the oligotrophic Pacific Ocean (Perry, 1972), in the Sargasso Sea (Rivkin and Swift, 1979), in coastal waters (Taft et al., 1977) and in lakes (Berman, 1970). Under conditions where ample dissolved phosphate is present for growth or intracellular concentration of the storage polyphosphate is high, synthesis of these enzymes is impaired. Because enzyme synthesis and activity is induced in response to... 

These ectoenzymes play a significant part in phosphorus cycling in natural waters. In lakes and oceans, phosphorus is partitioned among particulate and dissolved inorganic and organic fractions and is rapidly transformed from one fraction to another. Estimates of the size of the labile dissolved organic phosphorus pool in waters off the coast of Hawaii (0.01-0.2 /rg at P L 1), and its rapid turnover (0.008-0.04 h 1), presumably facilitated by extracellular phosphatases, are comparable with those of PO4- (Smith et al., 1985) and indicate the importance of ectoenzymes in the major nutrient cycles. 

Aaronson, S. and Patni, N.J. (1976) The role of surface and extracellular phosphatases in the phosphorus requirement of Ochromonas. Limnology and Oceanography 21,838-845. 

The identification of specific plant genes that encode extracellular phosphatase (Haran et al., 2000 Wasaki et al., 2000 Miller et al., 2001) provides new opportunities for investigating the significance of plant-derived enzymes through the development of reporter gene constructs, the use of specific probes, or the generation of modified plants that show enhanced or reduced phosphatase expression. 

Extracellular phosphatase activities from plant roots... 

Role of extracellular phosphatase in the phosphorus-nutrition of clover. Journal of Experimental Botany 44, 1 595-1 500. 

The ability of cyanobacteria to mobilize phosphate from insoluble inorganic materials is apparently widespread (Whitton, 2000), including calcium triphosphate (Bose et al., 1971), Mussoorie rock phosphate (Roychaudhury and Kaushik, 1989) and hydroxyapatite (Cameron and Julian, 1988). Several of these authors suggested that extracellular phosphatases might be involved, the most plausible example being that of a study by Natesan and Shanmuga-sundaram (1989) on an Anabaena strain grown with phosphate immobilized in soil. 

Nedoma, J, Strojsova, A., Vrba, J., Komarkova, J. and Simek, K. (2003) Extracellular phosphatase activity of natural plankton studied with ELF97 phosphate fluorescence quantification and labelling kinetics. Environmental Microbiology 5, 452 72. 

Strojsova, A., Vrba, j., Nedoma, j., Komarkova, j. and Znachor, P. (2003) Seasonal study of extracellular phosphatase expression in the phytoplankton of a eutrophic reservoir. European Journal of Phycology 38, 295-305. 

Whitton, B.A., Grainger, S.L.J., Hawley, G.R.W. and Simon, j.W. (1991) Cell-bound and extracellular phosphatase activities of cyanobacterial isolates. Microbial Ecology 21,85-98. 

Organic phosphorus and the remainder of the organic sulphur are associated with soil organic matter in the form of esters (i.e. C-O-P, C-O-S), and these nutrients are mineralized by the actions of various extracellular phosphatase and sulphatase enzymes ( biochemical mineralization ). 

The third most important nutrient phosphorous is taken up from the environment as orthophosphate. Phosphorous are generally strongly bound to compounds in the environment. It can be as phosphate containing organics or as insoluble salts in the soil or present as minerals in rocks. Fungi use extracellular phosphatases to liberate phosphorous from organics. They also produce organic acids to dissolve insoluble salts and rocks to be able to take up phosphorous. 

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