Rejsek K, Formanek P, Pavelka M
Department of Geology and Soil Science, Mendel University of Agriculture and Forestry, Brno, Czech Republic.
Amino Acids. 2008 Aug;35(2):411-7. doi: 10.1007/s00726-007-0601-5. Epub 2007 Nov 2.
The aim of this work was to modify the method of Ladd and Buttler (1972), by substituting Tris-HCl buffer (pH 8.52) with demineralized water (DEMI H(2)O), in order to assess its suitability for measurement of casein-protease activity at pH levels close to those of real soil in H(2)O. Measurements were undertaken over a range of incubation temperatures from 3 to 49 degrees C. Testing was performed on one organic soil and two different mineral soils. The substitution of Tris-HCl buffer by DEMI H(2)O at 49 degrees C decreased casein-protease activity to 67.25% in mineral soil and to 53.76% in organic soil. With decreasing temperature casein-protease activity decreased the most in organic soil, i.e., 0.07% of original its value at 3 degrees C. The incubation period was extended to maximally 336 h at 3 degrees C to totally obtain >10.0% of L-tyrosine equivalents released at optimum or close to optimum temperature and pH conditions. The Q(10) values of casein-protease activity measured after substituting Tris-HCl buffer with DEMI H(2)O were unexpectedly high. Between the temperatures of 3 and 49 degrees C Q(10) ranged from 3.46 to 4.25, whereas between 3 and 25 degrees C Q(10) ranged from 6.78 to 11.08. Therefore, the modified method of Ladd and Buttler (1972) presented can be used for measurement of soil casein-protease activity under pH conditions close to that of real soil pH and at an averaged soil temperatures measured in the field. This modification makes possible an expression of soil casein-protease activity potential - when being combined with measurements of casein-protease activity under optimum or close to optimum temperature and pH conditions, if high concentration of casein is present.
这项工作的目的是对Ladd和Buttler（1972年）的方法进行改进，用去离子水（DEMI H₂O）替代Tris-HCl缓冲液（pH 8.52），以评估其在接近H₂O中实际土壤pH值的条件下测量酪蛋白蛋白酶活性的适用性。测量在3至49摄氏度的一系列培养温度下进行。对一种有机土壤和两种不同的矿质土壤进行了测试。在49摄氏度下用DEMI H₂O替代Tris-HCl缓冲液后，矿质土壤中酪蛋白蛋白酶活性降至67.25%，有机土壤中降至53.76%。随着温度降低，有机土壤中酪蛋白蛋白酶活性下降最多，即在3摄氏度时降至其原始值的0.07%。在3摄氏度下培养期延长至最长336小时，以完全获得在最佳或接近最佳温度和pH条件下释放的L-酪氨酸当量的>10.0%。用DEMI H₂O替代Tris-HCl缓冲液后测得的酪蛋白蛋白酶活性的Q₁₀值出乎意料地高。在3至49摄氏度之间，Q₁₀值范围为3.46至4.25，而在3至25摄氏度之间，Q₁₀值范围为6.78至11.08。因此，所提出的对Ladd和Buttler（1972年）方法的改进可用于在接近实际土壤pH值的pH条件下以及在田间测得的平均土壤温度下测量土壤酪蛋白蛋白酶活性。这种改进使得在存在高浓度酪蛋白的情况下，结合在最佳或接近最佳温度和pH条件下的酪蛋白蛋白酶活性测量，能够表达土壤酪蛋白蛋白酶活性潜力成为可能。
