Phosphate acquisition by plants is an essential process that is directly implicated in the optimization of crop yields. Purple acid phosphatases (PAPs) are ubiquitous metalloenzymes, which catalyze the hydrolysis of a wide range of phosphate esters and anhydrides. While some plant PAPs display a preference for ATP as the substrate, others are efficient in hydrolyzing phytate or 2-phosphoenolpyruvate (PEP). PAP from red kidney bean (rkbPAP) is an efficient ATP- and ADPase, but has no activity towards phytate. Crystal structures of this enzyme in complex with ATP analogues (to 2.20 and 2.60 Å resolution, respectively) complement the recent structure of rkbPAP with a bound ADP analogue (ChemBioChem 20 (2019) 1536). Together these complexes provide the first structural insight of a PAP in complex with molecules that mimic biologically relevant substrates. Homology modeling was used to generate three-dimensional structures for the active sites of PAPs from tobacco (NtPAP) and thale cress (AtPAP26) that are efficient in hydrolyzing phytate and PEP as preferred substrates, respectively. The combining of crystallographic data, substrate docking simulations and a phylogenetic analysis of 49 plant PAP sequences (including the first PAP sequences reported from Eucalyptus) resulted in the identification of several active site residues that are important in defining the substrate specificities of plant PAPs; of particular relevance is the identification of a motif ("REKA") that is characteristic for plant PAPs that possess phytase activity. These results may inform bioengineering studies aimed at identifying and incorporating suitable plant PAP genes into crops to improve phosphorus acquisition and use efficiency. Organic phosphorus sources increasingly supplement or replace inorganic fertilizer, and efficient phosphorus use of crops will lower the environmental footprint of agriculture while enhancing food production.

中文翻译：

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调节植物紫色酸性磷酸酶底物特异性的结构元件：改善作物磷获取的途径

植物对磷酸盐的获取是一个重要的过程，直接涉及作物产量的优化。紫色酸性磷酸酶 (PAP) 是普遍存在的金属酶，可催化多种磷酸酯和酸酐的水解。虽然一些植物 PAP 偏爱 ATP 作为底物，但其他植物 PAP 可有效水解植酸或 2-磷酸烯醇丙酮酸 (PEP)。来自红芸豆的 PAP (rkbPAP) 是一种高效的 ATP 和 ADP 酶，但对植酸盐没有活性。这种酶与 ATP 类似物复合物的晶体结构（分别为 2.20 和 2.60 Å 分辨率）补充了 rkbPAP 与结合的 ADP 类似物的最新结构（ChemBioChem 20 (2019) 1536）。这些复合物共同提供了 PAP 与模拟生物相关底物的分子复合物的第一个结构洞察力。同源性建模用于生成来自烟草 (NtPAP) 和水芹 (AtPAP26) 的 PAP 活性位点的三维结构，它们分别有效地水解作为优选底物的植酸盐和 PEP。结合晶体学数据、底物对接模拟和 49 个植物 PAP 序列（包括从桉树报道的第一个 PAP 序列）的系统发育分析，鉴定了几个对定义植物 PAP 底物特异性很重要的活性位点残基；特别相关的是鉴定具有植酸酶活性的植物 PAP 所特有的基序（“REKA”）。这些结果可为旨在鉴定合适的植物 PAP 基因并将其整合到作物中以提高磷的获取和利用效率的生物工程研究提供信息。有机磷源越来越多地补充或替代无机肥料，作物磷的有效利用将降低农业的环境足迹，同时提高粮食产量。