The Importance of Enzyme Kinetics in the Temperature Sensitivity of Organic Matter Decomposition in Wetlands: II.

Recent developments of organic matter decomposition models highlighted the importance of enzyme kinetics with warming. Despite its critical importance to soil organic matter dynamics, measures of enzyme kinetic parameters (V_max and K_m) in wetland soils have not been well-investigated. To assess the effects of warming rate on enzyme kinetics from subtropical peat soils temperature the experiment was conducted by ramping up temperature @ 0.1°C day^-1 over the range of 15°C to 25°C.  Maximum velocity (V_max) of β-glucosidase (BG), leucine-amino peptidase (LAP), and phosphatase (PHO) increased from as a function of temperature, while enzyme efficiency (K_m) increased for BG and PHO but K_m decreased for LAP. Ratio of BG/LAP-V_max, BG/PHO-V_max decreased but LAP/PHO-V_max increased for all soils as a function of temperature. While, the ratio of BG/PHO-K_m and LAP/PHO-K_m decreased but BG/LAP-K_m increased at higher temp. Temperature sensitivity (Q₁₀) of enzymes was higher in the ramping phase over the 15°C acclimated phase (Q₁₀ increased of PHO, BG, and LAP increased @ 1.3-3, 1.2-1.8, 1.1-1.5 times, respectively). Findings suggested that an accurate representation of enzyme kinetics is an important step in predicting SOM dynamics as higher temperature can produce a different set of iso-enzymes compared to the lower temperature.