Pedosphere 31(1): 116--124, 2021
ISSN 1002-0160/CN 32-1315/P
©2021 Soil Science Society of China
Published by Elsevier B.V. and Science Press
Characterization of extracellular phosphatase activities in periphytic biofilm from paddy field
Shujie CAI1,2, Kaiying DENG1, Jun TANG1, Rui SUN1,2, Hailong LU1, Jiuyu LI1, Yonghong WU1, Renkou XU1
1Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008(China)
2College of Resources and Environment, University of Chinese Academy of Sciences, Beijing 100049(China)
      Periphytic biofilms exist widely in paddy fields, but their influences on the hydrolysis of organic phosphorus (P) have rarely been investigated. In this study, a periphytic biofilm was incubated in a paddy soil solution, and hydrolysis kinetic parameters (half-saturation constant (Km) and maximum catalytic reaction rate (Vmax)), optimal environmental conditions, substrate specificity, and response to different P regimes of the phosphatase activities in the periphytic biofilm were determined, in order to characterize extracellular phosphatase activities in periphytic biofilms from paddy fields. The results indicated that the periphytic biofilm could produce an acid phosphomonoesterase (PMEase), an alkaline PMEases, and a phosphodiesterase (PDEase). These three phosphatases displayed high substrate affinity, with Km values ranging from 141.03 to 212.96 μmol L-1. The Vmax/Km ratios for the phosphatases followed the order of alkaline PMEase > acid PMEase > PDEase, which suggested that the PMEases, especially the alkaline PMEase, had higher catalytic efficiency. The optimal pH was 6.0 for the acid PMEase activity and 8.0 for the PDEase activity, and the alkaline PMEase activity increased with a pH increase from 7.0 to 12.0. The optimal temperature was 50℃ for the PMEases and 60℃ for the PDEase. The phosphatases showed high catalytic efficiency for condensed P over a wide pH range and for orthophosphate monoesters at pH 11.0, except for inositol hexakisphosphate at pH 6.0. The inorganic P supply was the main factor in the regulation of phosphatase activities. These findings demonstrated that the periphytic biofilm tested had high hydrolysis capacity for organic and condensed P, especially under P-limited conditions.
Key Words:  hydrolysis capacity,kinetic parameters,optimal environmental conditions,phosphodiesterase,phosphomonoesterase,phosphorus hydrolysis,phosphorus supply,substrate specificity
Citation: Cai S J, Deng K Y, Tang J, Sun R, Lu H L, Li J Y, Wu Y H, Xu R K. 2021. Characterization of extracellular phosphatase activities in periphytic biofilm from paddy field. Pedosphere. 31(1): 116-124.
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