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采取北京山地黑桦林、刺槐林、板栗林、槲树林及山杨-白桦混交林5种阔叶林型下0～0.2m、0.2～0.4m、0.4～0.6m土层土壤,通过测定不同尿素浓度、培养时间及培养温度下酶促反应的放氨量,计算脲酶的各项动力学和热力学参数,探讨5种阔叶林型下土壤脲酶酶促反应特征。结果表明:各林型土壤脲酶酶促反应的动力学和热力学参数随温度升高和土壤深度增加而变化,反应过程中脲酶含量、酶-底物络合物形成难度、酶促反应速度以及形成过渡态络合物时参加反应的分子必须克服的势垒、所需的自由能、有序性等变化特征均有差异。不同林型下0～0.2m层土壤酶促反应的动力学和热力学特征表现不同,山杨-白桦混交林下土壤脲酶酶促反应表现出脲酶含量高、对底物的亲合力强,酶促反应需要克服的势垒较低、有序性增加最大和反应速度最快;板栗林下土壤表现出脲酶含量较低,对底物的亲合力最弱,需克服的能障最大,有序性增加幅度最小,酶促反应最慢;黑桦林、槲树林和刺槐林土壤酶促反应各项参数同上述林型变化不同。
The contents of 0 ~ 0.2m, 0.2 ~ 0.4m, 0.4 ~ 0.6m soil layers in five broad-leaved forest types of Betula platyphylla, Betula platyphylla, chestnut forest, Urea concentration, incubation time and ammonia release rate of the enzymatic reaction at culture temperature were calculated. The kinetic and thermodynamic parameters of urease were calculated, and the enzymatic characteristics of soil urease under five broad-leaved forest types were discussed. The results showed that the kinetic and thermodynamic parameters of urease enzymatic reaction varied with the increase of temperature and depth of soil. The urease content, the formation of enzyme-substrate complex, the reaction speed and the formation rate Transition state complexes to participate in the reaction of the molecules must overcome the barrier, the required free energy, orderliness and other characteristics are different. The dynamics and thermodynamic characteristics of soil enzymatic reactions in 0 ~ 0.2 m layer under different forest types show different performance. The enzymatic reaction of soil urease under the mixed forest of poplar and Betula platyphylla shows that the urease content is high, the affinity to substrate is strong, The potential barrier to be overcome in the reaction was lower, the orderliness increased and the reaction rate was fastest. The soil under chestnut showed lower urease content, the weaker affinity to the substrate, the largest energy barrier to be overcome and the orderliness The smallest increment and the slowest enzymatic reaction. The parameters of soil enzymatic reaction in black birch forest, oak forest and black locust forest were different from those in the above forest types.