Synthesis of methods used to assess soil protease activity
Synthesis of methods used to assess soil protease activity
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DOI：
10.1016/j.soilbio.2021.108277
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发表时间：
2021-04-30
影响因子：
9.7
通讯作者：
Jones, Davey L.
中科院分区：
文献类型：
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作者：
Greenfield, Lucy M.;Puissant, Jeremy;Jones, Davey L.
蛋白水解酶通过将蛋白质转化为寡肽和氨基酸，在土壤氮素循环中起着至关重要的作用。它们通常被视为陆地氮循环的瓶颈；因此，我们有可靠的方法来评估土壤中的蛋白酶活性，以了解蛋白酶活性的全球模式，这是至关重要的。针对这一点，已经开发了几种基于实验室的蛋白酶方法，并随后对其进行了修改。然而，这些不同方法的有效性在很大程度上仍然不得而知。此外，缺乏标准化的方案使得很难在不同研究之间比较蛋白酶活性。在这一系统的综合中，我们对最常用的比色法和荧光法用于测量土壤蛋白酶活性的方法进行了严格的评估，涉及680项独立研究和1491项单独检测。为了研究土壤蛋白酶活性的关键调控因素，我们收集了环境因素(年平均温度和土壤pH)和方法因素(测定温度和pH)的相关元数据。用比色底物测得的蛋白酶活性集中在约1000nmol产物g(-1)h(-1)左右，而用荧光底物测得的酶活较低，约为100nmol产物g(-1)h(-1)。荧光和比色底物针对不同的蛋白酶，可能具有不同的丰度、动力学参数、催化机理或生态功能，这表明为什么比色底物具有更高的蛋白酶活性。我们发现，在这些峰值附近，土壤蛋白水解酶活性变化很大，可能是由于可能影响/偏差结果的广泛的环境或方法因素所致。我们提出了以下测量土壤蛋白酶活性的建议：1)报告分析条件和土壤特性，特别是pH和温度，2)在田间或优化的pH和温度条件下进行分析，以及3)检查测量结果是否在0到5000 nmol产物g(-1)h(-1)之间。这将有助于减少因方法偏差而导致的土壤蛋白酶活性测量的差异，并改进非生物和生物相关数据的报告。总而言之，这将导致更好地理解蛋白酶活性的生态驱动因素，并完善全球生物地球化学模型的参数化。
Proteases play a crucial role in the soil nitrogen (N) cycle by converting protein to oligopeptides and amino acids. They are often viewed as a bottleneck in terrestrial N cycling; therefore, it is vital that we have robust methods for evaluating protease activity in soil to understand global patterns of protease activity. In response to this, several laboratory-based protease methods have been developed and subsequently modified. However, the validity of these different approaches remains largely unknown. In addition, the lack of standardised protocols makes it difficult to compare protease activity across studies. In this systematic synthesis, we critically evaluate the most common colorimetric and fluorimetric methods used to measure soil protease activity involving 680 independent studies and 1,491 individual assays. To investigate the key regulators of soil protease activity, we collected associated metadata on environmental (mean annual temperature and soil pH) and methodological (assay temperature and pH) factors. Protease activity measured with colorimetric substrates were centred around ca. 1000 nmol product g(-1) h(-1), whilst rates measured with fluorimetric substrates were lower at ca. 100 nmol product g(-1) h(-1). Fluorimetric and colorimetric substrates target different proteases which are likely to have different abundances, kinetic parameters, catalytic mechanism or ecological function suggesting why colorimetric substrates have a higher protease activity. We found soil protease activity varied widely around these peaks, likely due to a wide range of environmental or methodological factors that may influence/bias the result. We present the following recommendations for measuring soil protease activity: 1) report assay conditions and soil characteristics, particularly pH and temperature, 2) conduct the assay at either field or optimised pH and temperature conditions, and, 3) check that measurements lie between 0 and 5000 nmol product g(-1) h(-1). This will help reduce the variation in soil protease activity measurements due to methodological bias and improve reporting of abiotic and biotic associated data. Altogether this will lead to a better understanding of the ecological drivers of protease activity and refine parameterisation of global biogeochemical models.