This view shows enzymes only for those organisms listed below, in the list of taxa known to possess the pathway. If an enzyme name is shown in bold, there is experimental evidence for this enzymatic activity.
|Superclasses:||Degradation/Utilization/Assimilation → Inorganic Nutrients Metabolism → Phosphorus Compounds Metabolism|
Some taxa known to possess this pathway include : Arabidopsis thaliana col [Tran10], Burkholderia cenocepacia J2315, Glycine max, Ipomoea batatas, Medicago truncatula, Solanum lycopersicum, Solanum tuberosum, Zea mays
Plant growth and development requires macro and micronutrients, some of which are available only from external sources like the soil in which they grow. Phosphorous is one such essential macronutrient, it is usually absorbed and utilized by the plants in the form of phosphate (also known as inorganic phosphate, or Pi) [Yuan08]. Many soils are deficient in phosphate, leading to phosphate starvation for plants growing in them. Plants develop several strategies to overcome phosphate limitation, including morphological, biochemical and physiological responses to enhance the acquisition of this vital macronutrient. These combined responses enhance the chances of plants to survive the prospects of phosphate starvation. Due to continous leaching, ancient soils are known to become limited in the availability of phosphate.
Once absorbed, the phosphate is utilized inside the cells at optimum cellular concentration for the various developmental and biochemical processes. Phosphate acquisition is a complicated process and has various modified routes. The phosphate homeostasis is maintained by acquisition, limited consumption and effective recycling, when the supply and demand is not equitable. The molecular basis for these strategies is being studied in a number of species [Lin09]. The Gulf Ryegrass is an ideal model plant as it hyperaccumulates phosphate utilizing multiple acquisition and mobilization systems under varying phosphate regimes [Vanninen91]. In some plants the chief enzymes that partcipate in the transport and recycling of phosphate are developmentally regulated [Li02].
About This Pathway
The Purple Acid Phosphatases (PAP's) are said to play a role in phosphate salvaging when cells are depleted or starved of phosphate and under oxidative stress. Thus PAP's are crucial for the cellular metabolism and energy transduction processes. PAP's have also been isolated from mammalian and fungal sources, although the physiological function of these enzymes has yet to be established [Schenk99]. Genes encoding such enzymes are also present in some bacteria, including cyanobacteria, but their role is not clear. It has been suggested that they prevent damage caused by generated by invaded host cells (mycobacteria) or by the light-harvesting complex (cyanobacteria) [Schenk00]. However, the enzyme of Burkholderia cenocepacia J2315 is induced by lack of phosphate and excreted from the cell, suggesting it may be involved in phosphate acquisition [Yeung09].
The PAP enzymes may exist in two forms: the inactive purple form, where the redox-active iron is in the ferric state, and the active pink form, where the iron is reduced to the ferrous state.The PAP's are expressed in a tissue specific manner and often exist as isozymes [Zhu05, Zimmermann04]. The isozymes exhibit variation in molecular structure, substrate specficity and localization.
Some PAP's, such as alkaline peroxidase / purple acid phosphatase from Solanum lycopersicum, are multifunctional enzymes that have both a purple acid phosphatase and an alkaline peroxidase function. These enzymes are hypothesized to function in the production of reactive oxygen species (ROS) [Bozzo02]. The phosphatase and oxygen radical-generating activities of PAP's are functionally independent, similar to those of mammalian PAP [Kaija02].
Bozzo02: Bozzo GG, Raghothama KG, Plaxton WC (2002). "Purification and characterization of two secreted purple acid phosphatase isozymes from phosphate-starved tomato (Lycopersicon esculentum) cell cultures." Eur J Biochem 269(24);6278-86. PMID: 12473124
Kaija02: Kaija H, Alatalo SL, Halleen JM, Lindqvist Y, Schneider G, Vaananen HK, Vihko P (2002). "Phosphatase and oxygen radical-generating activities of mammalian purple acid phosphatase are functionally independent." Biochem Biophys Res Commun 292(1);128-32. PMID: 11890682
Li02: Li D, Zhu H, Liu K, Liu X, Leggewie G, Udvardi M, Wang D (2002). "Purple acid phosphatases of Arabidopsis thaliana. Comparative analysis and differential regulation by phosphate deprivation." J Biol Chem 277(31);27772-81. PMID: 12021284
Schenk99: Schenk G, Ge Y, Carrington LE, Wynne CJ, Searle IR, Carroll BJ, Hamilton S, de Jersey J (1999). "Binuclear metal centers in plant purple acid phosphatases: Fe-Mn in sweet potato and Fe-Zn in soybean." Arch Biochem Biophys 370(2);183-9. PMID: 10510276
Tran10: Tran HT, Qian W, Hurley BA, She YM, Wang D, Plaxton WC (2010). "Biochemical and molecular characterization of AtPAP12 and AtPAP26: the predominant purple acid phosphatase isozymes secreted by phosphate-starved Arabidopsis thaliana." Plant Cell Environ 33(11);1789-803. PMID: 20545876
Vanninen91: Vanninen E, Uusitupa M, Siitonen O, Laitinen J, Lansimies E, Pyorala K (1991). "Effect of diet therapy on maximum aerobic power in obese, hyperglycaemic men with recently diagnosed type 2 diabetes." Scand J Clin Lab Invest 51(3);289-97. PMID: 1882180
Yeung09: Yeung SL, Cheng C, Lui TK, Tsang JS, Chan WT, Lim BL (2009). "Purple acid phosphatase-like sequences in prokaryotic genomes and the characterization of an atypical purple alkaline phosphatase from Burkholderia cenocepacia J2315." Gene 440(1-2);1-8. PMID: 19376213
Zhu05: Zhu H, Qian W, Lu X, Li D, Liu X, Liu K, Wang D (2005). "Expression patterns of purple acid phosphatase genes in Arabidopsis organs and functional analysis of AtPAP23 predominantly transcribed in flower." Plant Mol Biol 59(4);581-94. PMID: 16244908
Zimmermann04: Zimmermann P, Regierer B, Kossmann J, Frossard E, Amrhein N, Bucher M (2004). "Differential expression of three purple acid phosphatases from potato." Plant Biol (Stuttg) 6(5);519-28. PMID: 15375722
Hurley10: Hurley BA, Tran HT, Marty NJ, Park J, Snedden WA, Mullen RT, Plaxton WC (2010). "The dual-targeted purple acid phosphatase isozyme AtPAP26 is essential for efficient acclimation of Arabidopsis to nutritional phosphate deprivation." Plant Physiol 153(3);1112-22. PMID: 20348213
Kaida03: Kaida R, Sage-Ono K, Kamada H, Okuyama H, Syono K, Kaneko TS (2003). "Isolation and characterization of four cell wall purple acid phosphatase genes from tobacco cells." Biochim Biophys Acta 1625(2);134-40. PMID: 12531472
Passariello06: Passariello C, Forleo C, Micheli V, Schippa S, Leone R, Mangani S, Thaller MC, Rossolini GM (2006). "Biochemical characterization of the class B acid phosphatase (AphA) of Escherichia coli MG1655." Biochim Biophys Acta 1764(1);13-9. PMID: 16297670
Rossolini94: Rossolini GM, Thaller MC, Pezzi R, Satta G (1994). "Identification of an Escherichia coli periplasmic acid phosphatase containing of a 27 kDa-polypeptide component." FEMS Microbiol Lett 118(1-2);167-73. PMID: 8013875
Thaller97: Thaller MC, Schippa S, Bonci A, Cresti S, Rossolini GM (1997). "Identification of the gene (aphA) encoding the class B acid phosphatase/phosphotransferase of Escherichia coli MG1655 and characterization of its product." FEMS Microbiol Lett 1997;146(2);191-8. PMID: 9011040
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