ABSTRACT This study investigated the relationship between a recently proposed alkaline hydrolysis method for estimating the chemical index of nitrogen (N) mineralization potential of soils and the activities of arylamidase and four amidohydrolases involved in hydrolysis of organic N (ON) in soils. Nitrogen mineralization was studied in 13 soils from uncultivated fields in Iowa, USA, by direct steam distillation of 1 g field-most soil treated with 1 M KOH or 1 M NaOH. The distillate was collected in boric acids, which was changed every 5 min for a total of 40 min. The NH4 +-N in the distillate was determined by titration with 0.005 M H2SO4. The cumulative amounts of N hydrolyzed were fitted to the first-order exponential equation to determine the “potentially hydrolyzable N (Nmax )” for the soils. The activities of arylamidase, L-asparaginase, L-glutaminase, amidase, and L-aspartase were assayed at their optimal pH values. Results showed that estimated Nmax values were strongly correlated with the activities of arylamidase and amidohydrolases. The activities of arylamidase and the amidohydrolases were significantly correlated, indicating that the activities of the two groups of enzymes are coupled in mineralization of ON in soils. Based on the specificity of enzyme reactions and the strong relationship between estimated Nmax values and the activities of arylamidase and amidohydrolases, we concluded that similar amide-N bonds were susceptible to enzymatic and alkaline hydrolysis, and that alkaline hydrolyzable ON can be used as an index of N mineralization in soils.

中文翻译：

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作为土壤中氮矿化指标的碱性可水解有机氮：与芳基酰胺酶和酰胺水解酶活性的关系

摘要 本研究调查了最近提出的用于估算土壤氮 (N) 矿化潜力化学指数的碱性水解方法与参与土壤中有机氮 (ON) 水解的芳基酰胺酶和四种酰胺水解酶的活性之间的关系。通过直接蒸汽蒸馏用 1 M KOH 或 1 M NaOH 处理过的 1 g 田间土壤，对来自美国爱荷华州未开垦田地的 13 种土壤的氮矿化进行了研究。馏出液收集在硼酸中，每 5 分钟更换一次，总共 40 分钟。馏出物中的 NH4 +-N 通过用 0.005 M H2SO4 滴定确定。水解氮的累积量符合一阶指数方程，以确定土壤的“潜在水解氮（Nmax）”。芳基酰胺酶、L-天冬酰胺酶、L-谷氨酰胺酶、酰胺酶和L-天冬氨酸酶在其最佳pH值下进行测定。结果表明，估计的 Nmax 值与芳基酰胺酶和酰胺水解酶的活性密切相关。芳基酰胺酶和酰胺水解酶的活性呈显着相关，表明这两组酶的活性在土壤ON矿化中是耦合的。基于酶反应的特异性以及估计的 Nmax 值与芳基酰胺酶和酰胺水解酶活性之间的强相关性，我们得出结论，相似的酰胺-N 键对酶促和碱水解敏感，可以将碱水解 ON 作为指标土壤中氮的矿化作用。结果表明，估计的 Nmax 值与芳基酰胺酶和酰胺水解酶的活性密切相关。芳基酰胺酶和酰胺水解酶的活性呈显着相关，表明这两组酶的活性在土壤ON矿化中是耦合的。基于酶反应的特异性以及估计的 Nmax 值与芳基酰胺酶和酰胺水解酶活性之间的强相关性，我们得出结论，相似的酰胺-N 键对酶促和碱水解敏感，可以将碱水解 ON 作为指标土壤中氮的矿化作用。结果表明，估计的 Nmax 值与芳基酰胺酶和酰胺水解酶的活性密切相关。芳基酰胺酶和酰胺水解酶的活性呈显着相关，表明这两组酶的活性在土壤ON矿化中是耦合的。基于酶反应的特异性以及估计的 Nmax 值与芳基酰胺酶和酰胺水解酶活性之间的强相关性，我们得出结论，相似的酰胺-N 键对酶促和碱水解敏感，可以将碱水解 ON 作为指标土壤中氮的矿化作用。表明两组酶的活性在土壤中 ON 的矿化中是耦合的。基于酶反应的特异性以及估计的 Nmax 值与芳基酰胺酶和酰胺水解酶活性之间的强相关性，我们得出结论，相似的酰胺-N 键对酶促和碱水解敏感，可以将碱水解 ON 作为指标土壤中氮的矿化作用。表明两组酶的活性在土壤中 ON 的矿化中是耦合的。基于酶反应的特异性以及估计的 Nmax 值与芳基酰胺酶和酰胺水解酶活性之间的强相关性，我们得出结论，相似的酰胺-N 键对酶促和碱水解敏感，可以将碱水解 ON 作为指标土壤中氮的矿化作用。