Enzymatic hydrolysis of soil organic phosphorus by immobilized phosphatases

In order to estimate the role of phosphatases in maintaining the potential bioavailable P pool in soils, water and 0.4M NaOH soil extracts were incuba ted with immobilized acid phosphatase, alkaline phosphatase, phospholipase and nuclease, separately, and in combinations. Immobilized nuclease at an o ptimum pH of 7.0 hydrolyzed the most soluble unreactive P (SUP) both in wat er and 0.4M NaOH extracts. The combination of immobilized alkaline phosphat ase and nuclease increased the hydrolysis of SUP at pH 7.0 by up to 61% in 0.4M NaOH extracts relative to that due to immobilized nuclease alone. The combination of immobilized acid phosphatase and nuclease, however, did not increase the hydrolysis of SUP in either extract relative to that due to im mobilized nuclease alone. Immobilized alkaline phosphatase and phospholipas e increased the hydrolysis of SUP at pH 7.0 by up to 49% in 0.4M NaOH extra cts relative to that due to immobilized phospholipase alone. Similarly, imm obilized acid phosphatase and phospholipase increased the hydrolysis of SUP at pH 7.0 by up to 49% in 0.4M NaOH extracts relative to that: due to immo bilized phospholipase alone. The similarities in the optimum pH of indigeno us phosphatases in soils and the immobilized phosphatases used in this stud y, immobilized on positively charged supports, suggests that indigenous pho sphatases could be immobilized on positively charged surfaces in soils.