Considerations on the use of the p-nitrophenyl phosphomonoesterase assay in the study of the phosphorus nutrition of soil borne fungi.
The p-nitrophenyl phosphomonoesterase assay (pNPPase) is commonly used to measure cell-wall-associated and extracellular phosphatase activity of soil fungi. pNPPases are usually assayed in the context of fungal nutrition, where inorganic P supply might be enhanced by the mineralisation of monoester organic P sources in the soil. The importance of the assay to the P nutrition of soil fungi is considered based on the evidence currently available including the consistency of methodological approach. The nature of organic P in the soil and the relevance of the assay to some specific soil substrates is discussed, particularly the chemistry and bioavailability of myo-inositol hexakisphosphate and the lower inositol phosphates. The evidence for the long-term stability of pNPPases in the soil is examined in the light of the persistence of pNPPase in soils. The role of persistent extracellular fungal pNPPases in the soil P cycle is discussed. Conclusions from pNPPase based studies must be based upon an appreciation of the constraints of the assay and the complex chemistry of organic P and pNPPase in the soil.
Tibbett
Mark
M
CSIRO Land and Water, Davies Laboratory, Townsville, Queensland, Australia. mark.tibbett@csiro.au
D005658:Fungi / Q000187:drug effects / Q000201:enzymology* / Q000254:growth & development; D006863:Hydrogen-Ion Concentration; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism*; D010758:Phosphorus / Q000378:metabolism* / Q000494:pharmacology; D012988:Soil Microbiology; D013696:Temperature
D010758:Phosphorus; D010744:Phosphoric Monoester Hydrolases