Enzymes Involved in Phosphorus Metabolism

The importance of phosphatases for plant nutrition has repeatedly been pointed out (Cosgrove 1967; Ramirez-Martinez 1968; Halstead and McKercher 1975; Hayman 1975; Kiss et al. 1975; Cosgrove 1977; Dalai 1977; Speir and Ross 1978, Dick and Tabatabai 1987). In most soils, the organically bound P-fraction is higher than the inorganic. Among the organic phosphoric acid esters, the largest fraction in the soil is phytanic acid or phytin (Halstead and McKercher 1975; Speir and Ross 1978). Phophorus uptake by plants requires mineralization of the organic P-component by phosphatases to orthophosphate (Speir and Ross 1978; Malcolm 1983). Phosphatases are inducible enzymes that are produced predominantly under conditions of low phosphorus availability. Phosphatases are excreted by plant roots and by microorganisms. Microbial phosphatases dominate in soils.