Is the enzymatic hydrolysis of soil organic phosphorus compounds limited by enzyme or substrate availability?

Publication date: Available online 15 October 2019Source: Soil Biology and BiochemistryAuthor(s): K.A. Jarosch, E. Kandeler, E. Frossard, E.K. BünemannAbstractThe mineralization of soil organic phosphorus (P) is catalysed by extracellular phosphatases that hydrolyse different non-phytate phosphomonoesters (e.g., sugar phosphates and nucleotides), inositol phosphates (e.g., phytic acids), and phosphodiesters (e.g., nucleic acids, phospholipids). The availabilities of both the organic P compound and the respective phosphatase enzyme jointly determine whether the hydrolysis reaction is substrate limited (enzyme availability > substrate availability) or enzyme limited (enzyme availability < substrate availability), with potential consequences for overall organic P composition and accumulation in soil. Our objective was to evaluate whether the hydrolysis of various organic P compounds in soil is limited by availability of substrate or enzyme. To this end, we combined the principles of enzyme activity assays and enzyme addition assays. Ten soils with contrasting properties and origins received either model organic P substrate, specific phosphatases or a combination of both, added either to a soil:water suspension or a soil:water filtrate. Soil indigenous activity of phosphatases was low in all filtrates, confirming that enzymes were mostly associated with the solid fraction of the soil. In soil suspensions, the rapid hydrolysis of added non-phytate phosphomonoester sub...
Source: Soil Biology and Biochemistry - Category: Biology Source Type: research