石油污染土壤多酚氧化酶的动力学及热力学特征

土壤多酚氧化酶是一种氧化还原酶，能够将土壤中芳香族化合物氧化成醌，促进土壤中石油类物质的分解转化.以距大庆油田工作区不同距离（1、5、15 km）的石油污染地为对象，研究不同温度下石油污染裸地及羊草（Leymus chinensis）修复地的土壤多酚氧化酶活性及其动力学和热力学特征的变化.结果表明:土壤多酚氧化酶活性随温度和底物浓度的增加而逐渐增大，在温度为30℃或40℃、底物浓度为80 mmol/L或160 mmol/L时达到最大值；各样地土壤酶的动力学参数K_m（Mihaelis常数）随温度的变化规律不同，V_max（酶促反应最大速度）和V_max/K_m（催化效率）随温度升高而逐渐增大，均在30℃或40℃时达到最大值；热力学参数Q₁₀（温度系数）、ΔH（活化焓）、ΔS（活化熵）随温度变化差异不显著，ΔG（活化自由能）随温度升高呈逐渐增加趋势.在同一温度下，石油污染裸地土壤多酚氧化酶活性高于羊草修复地；K_m和V_max/K_m在各样地均表现为无规律性变化，V_max最大值出现在距油田工作区5 km处的裸地（BMP），最小值出现在距油田工作区5 km处的羊草修复地（LMP）；Q₁₀、E_a（活化能）、ΔH、ΔS的最大值均出现在距油田工作区1 km处的裸地（BVP），最小值均出现在距油田工作区1 km处的羊草修复地（LVP）.研究显示，升温和植物修复对土壤多酚氧化酶活性的反应特征有较大影响. 

Kinetic and Thermodynamic Properties of Polyphenol Oxidase in Petroleum Contaminated Soil

Soil polyphenol oxidase (PPO) is an oxidoreductase that can oxidize aromatic compounds in the soil to quinones and promote the decomposition and transformation of petroleum-based substances in the soil. The changes of soil PPO activity and its kinetic and thermodynamic properties of petroleum polluted bare lands and Leymus chinensis remediation land at different temperatures were studied in petroleum contaminated sites at different distance (1, 5, 15 km) from the working area of Daqing oilfield. The results showed that the activity of soil PPO increased gradually with the increase of temperature and substrate concentration, and reached the maximum when the temperature was 30 ℃ or 40 ℃ and the substrate concentration was 80 mmol/L or 160 mmol/L. The variation of soil dynamic parameter K_m (Mihaelis constant) with temperature in different areas was different and V_max (maximum speed of enzyme reaction) and V_max/K_m (catalytic efficiency) increased gradually with the increase of temperature and reached the maximum at 30 ℃ or 40 ℃. The thermodynamic parameters Q₁₀(temperature coefficient), ΔH (activation enthalpy), ΔS(activation entropy) had no significant difference with temperature changes, but ΔG (free energy of activation) increased gradually with increasing temperature. At the same temperature, the activity of PPO in petroleum polluted bare lands was higher than that in L. chinensis remediation land, K_m and V_max/K_m showed irregular changes in all plots, but the maximum value of V_max occurred in the bare land 5 km away from the oil field working area (BMP) and the minimum value appeared in the L. chinensis remediation land 5 km away from oil field working area (LMP). The maximum values of Q₁₀, E_a (activation energy), ΔH and ΔS all appeared in the bare land 1 km away from the oilfield working area (BVP) and the minimum values appeared in the L. chinensis remediation land 1 km away from oil field working area (LVP). The above results indicate that warming and phytoremediation have a greater impact on the response characteristics of soil PPO activity.