Effect of citrate on Aspergillus niger phytase adsorption and catalytic activity in soil
Effect of citrate on Aspergillus niger phytase adsorption and catalytic activity in soil
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DOI：
10.1016/j.geoderma.2017.06.015
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发表时间：
2017-11-01
期刊：
影响因子：
6.1
通讯作者：
Haygarth, Philip M.
中科院分区：
文献类型：
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作者：
Mezeli, Malika M.;Menezes-Blackburn, Daniel;Haygarth, Philip M.
已知来自细菌、真菌和植物根系分泌物的植酸酶水解土壤中的有机磷（P-o）为生物可利用的无机正磷酸盐。在农业系统中利用这种生物化学功能，提供了替代可持续磷源的潜力。植酸酶吸附到土壤颗粒和植酸金属络合已被证明抑制植酸（InsP（6））脱磷酸化。有机酸阴离子如柠檬酸盐增加植酸酶对InsP（6）复合形式的催化效率，但机制知之甚少。本研究的目的是评估尼日尔植酸酶的失活及其催化性质的变化，以及柠檬酸盐对植酸酶吸附和对游离、沉淀和吸附InsP（6）的活性的影响。我们进行了一系列的酶水解活性测定，当酶在不同的化学条件下，在土壤溶液中和吸附到土壤中时，有和没有柠檬酸盐。A.尼日尔植酸酶对Cambisol测试土壤表现出相对较低的吸收亲和力。吸附使植酸酶活性降低37.3%。柠檬酸盐对植酸酶的吸附速率、吸附总量及土壤吸附植酸酶活性均无影响。游离植酸酶和土壤溶液中的植酸酶在pH4.5 -5.5时活性最高（>= 80%）。在pH依赖性曲线中，与游离酶或土壤溶液pH> 5和< 4中的酶相比，土壤吸附酶的活性略有下降。只有在离子强度（NaCl）> 0.6 M时，吸附和游离酶的活性才降低，而土壤溶液中酶的活性在所有测试的离子强度下都降低。当植酸酶处于游离状态时，纤毛虫显著提高了植酸酶对吸附在土壤上的InsP（6）的活性（p
Phytase enzymes from bacteria, fungus and plant root exudates are known to hydrolyse organic phosphorus (P-o) to bioavailable inorganic orthophosphate in soil. Exploiting such biochemical functions in agricultural systems, offers the potential for alternative sustainable phosphorus sources. Phytase adsorption to soil particles and phytate metal complexation has been shown to inhibit phytate (InsP(6)) dephosphorylation. Organic acid anions such as citrate increase phytase catalytic efficiency towards complexed forms of InsP(6), but the mechanisms are poorly understood. The aim of this work was to evaluate Aspergillus niger phytase inactivation and changes in its catalytic properties upon addition to soil, as well as the effect of citrate on phytase adsorption and activity towards free, precipitated and adsorbed InsP(6).We performed a series of enzyme hydrolysis activity assays when the enzymes were free, in soil solution and adsorbed to soil under varying chemical conditions, with and without citrate. A. niger phytase showed a relatively low absorption affinity for the Cambisol test soil. Phytase activity reduced by 37.3% due to adsorption. Citrate had no effect on the rate or total amount of phytase adsorption or soil adsorbed phytase activity thereafter. Free phytases and phytases in soil solution showed optimum activity (>= 80%) at pH 4.5-5.5. Activity decreased slightly for soil adsorbed enzymes compared to enzymes which were free or in soil solution > pH 5 and < 4 in the pH dependency curve. A decrease in activity was seen only at ionic strengths (NaCl) > 0.6 M in adsorbed and free enzymes, while activity from enzymes in soil solution reduced in all tested ionic strengths. Ciliate significantly increased phytase activity towards InsP(6) adsorbed to soil when the phytases were free (p