Nonlinear responses of the Vmax and Km of hydrolytic and polyphenol oxidative enzymes to nitrogen enrichment

Publication date: Available online 5 November 2019Source: Soil Biology and BiochemistryAuthor(s): Weixing Liu, Rui Tian, Ziyang Peng, Sen Yang, Xiao xiao Liu, Yashu Yang, Wenhao Zhang, Lingli LiuAbstractThe kinetics of soil microbial extracellular enzymes are important in regulating soil organic matter decomposition and ecosystem function. However, it is still unclear how the kinetic parameters (Vmax and Km) of hydrolytic and polyphenol oxidative enzymes respond to increased nitrogen (N) deposition and to what extent they regulate microbial respiration under N enrichment. We measured the Vmax and Km of seven soil hydrolytic enzymes and polyphenol oxidase (PPO) in a temperate steppe after 15 years of multi-level N addition treatments. Soil microbial respiration and physicochemical properties in the steppe were also monitored. The results showed that soil microbial respiration decreased exponentially with increasing N addition. The Vmax of carbon (C)-degrading and N-degrading hydrolytic enzymes decreased and the Vmax of acid phosphatase (AP) increased with increasing N addition. The reduction in the Vmax of C- and N-degrading hydrolytic enzymes was primarily caused by the decrease in soil pH under N enrichment. The Km of most hydrolytic enzymes decreased, expect for the Km of AP and β-xylosidase (BX), which increased with increasing N addition. As N addition increased, Vmax and Km of PPO first increased, maximized at 8 g N m−2 y−1, and then decreased. We conducted mode...
Source: Soil Biology and Biochemistry - Category: Biology Source Type: research