Factors affecting invertase activity in soils
Factors affecting invertase activity in soils
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DOI：
10.1007/bf02181349
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发表时间：
1983-10
期刊：
影响因子：
4.9
通讯作者：
W. Frankenberger;J. Johanson
中科院分区：
文献类型：
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作者：
W. Frankenberger;J. Johanson
通过转化酶活性释放还原糖的速率显示缓冲pH为5.0的最佳。一般来说，在最佳pH范围附近，转化酶活性的下降是由于可逆反应，涉及蛋白质活性中心官能团的电离或去电离，但在高酸性或碱性条件下（pH<4至>.9），活性的降低似乎是由于酶的不可逆失活。该反应与酶的量呈线性关系，直至3 g土壤。通过改变底物浓度，发现在土壤中加入145mm蔗糖溶液时，该酶的反应速率接近零级动力学。Michaelis-Menten方程的三次线性变换表明，不同土壤的表观km常数不同，但三幅图的结果相似。通过Lineweaver-Burk图，5种土壤的km值范围为16.3 ~ 42.1（平均g =24.5）， vmax值范围为1.98 ~ 7.37 mg /g土壤/24 h。土壤中转化酶活性的最佳温度为50℃，酶的变性开始于55℃。转化酶活性的活化能（Ea）和激活焓（ΔH*）值分别为6.1 ~ 43.1和3.5 ~ 40.5，单位为kJ/mol。在温度为10 ~ 50℃的土壤中，转化酶的q10值为1.08 ~ 1.96。在标准条件下，还原糖的积累与时间呈线性关系，最长可达48 h。在影响土壤转化酶活性的各种预处理中，甲苯、TCA和PMA对酶的平均抑制率分别为19%、54%和11%。蒸汽灭菌基本上破坏了土壤中的转化酶。
The rate of reducing sugars released through invertase activity exhibited a buffer pH optimum of 5.0. Generally, the decline in invertase activity in its pH-profile near the optimal pH range was due to a reversible reaction that involved ionization or deionization of the functional groups in the active centre of the protein, but under highly acidic or alkaline conditions (pH<4 to >9) the reduced activity appears to be due to irreversible inactivation of the enzyme. The dependence of the reaction on the amount of enzyme present was linear up to 3 g of soil. By varying the substrate concentration, it was found that the reaction rate of this enzyme approached zero-order kinetics when 145mMof sucrose solution was added to soils. Application of three linear transformations of the Michaelis-Menten equation indicated that the apparent Kmconstants varied among the soils studied, but the results obtained by the three plots were similar. By using the Lineweaver-Burk plot, the Kmvalues in five soils ranged from 16.3 to 42.1 (avg.=24.5) mMand Vmaxvalues ranged from 1.98 to 7.37 mg of reducing sugars released/g of soil/24 h. The optimum temperature for invertase activity in soils was observed at 50°C and denaturation of the enzyme began at 55°C. The activation energy (Ea) and enthalpy of activation (ΔH*) values for invertase activity, expressed in kJ/mole, ranged from 6.1 to 43.1 and 3.5 to 40.5, respectively. The Q10values for the invertase reaction in soils with a temperature range to 10 to 50°C ranged from 1.08 to 1.96. Under standerd conditions, the accumulation of reducing sugars was linear with time up to 48 h. Among the various pretreatments that affected invertase activity in soils, toluene, TCA, and PMA inhibited the enzyme by an average of 19, 54, and 11%, respectively. Steam-sterilization essentially destroyed soil invertase.