Functional Genomics, Biochemistry and Plant Physiology, Instituto de Ciencias Biológicas, Universidad de Talca, Campus Lircay s/n, Talca, Chile; Multidisciplinary Agroindustry Research Laboratory, Instituto de Ciencias Biomédicas, Universidad Autónoma de Chile, 5 poniente #1670, Talca, Chile.
Functional Genomics, Biochemistry and Plant Physiology, Instituto de Ciencias Biológicas, Universidad de Talca, Campus Lircay s/n, Talca, Chile.
Plant Physiol Biochem. 2019 Mar;136:155-161. doi: 10.1016/j.plaphy.2019.01.016. Epub 2019 Jan 19.
Xyloglucan endotransglycosylase/hydrolases (XTH) may have endotransglycosylase (XET) and/or hydrolase (XEH) activities. Previous studies confirmed XET activity for PrXTH1 protein from radiata pine. XTHs could interact with many hemicellulose substrates, but the favorite substrate of PrXTH1 is still unknown. The prediction of union type and energy stability of the complexes formed between PrXTH1 and different substrates (XXXGXXXG, XXFGXXFG, XLFGXLFG and cellulose) were determined using bioinformatics tools. Molecular Docking, Molecular Dynamics, MM-GBSA and Electrostatic Potential Calculations were employed to predict the binding modes, free energies of interaction and the distribution of electrostatic charge. The results suggest that the enzyme formed more stable complexes with hemicellulose substrates than cellulose, and the best ligand was the xyloglucan XLFGXLFG (free energy of -58.83 ± 0.8 kcal mol). During molecular dynamics trajectories, hemicellulose fibers showed greater stability than cellulose. Aditionally, the kinetic properties of PrXTH1 enzyme were determined. The recombinant protein was active and showed an optimal pH 5.0 and optimal temperature of 37 °C. A Km value of 20.9 mM was determined for xyloglucan oligomer. PrXTH1 is able to interact with different xyloglycans structures but no activity was observed for cellulose as substrate, remodeling cell wall structure in response to inclination.
木葡聚糖内转糖基酶/水解酶（XTH）可能具有内转糖基酶（XET）和/或水解酶（XEH）活性。先前的研究证实了辐射松 PrXTH1 蛋白的 XET 活性。XTH 可以与许多半纤维素底物相互作用，但 PrXTH1 的首选底物仍不清楚。使用生物信息学工具预测了 PrXTH1 与不同底物（XXXGXXXG、XXFGXXFG、XLFGXLFG 和纤维素）形成的复合物的连接类型和能量稳定性。采用分子对接、分子动力学、MM-GBSA 和静电势计算来预测结合模式、相互作用的自由能和静电电荷的分布。结果表明，该酶与半纤维素底物形成的复合物比纤维素更稳定，最佳配体是木葡聚糖 XLFGXLFG（-58.83 ± 0.8 kcal/mol）。在分子动力学轨迹中，半纤维素纤维比纤维素更稳定。此外，还测定了 PrXTH1 酶的动力学特性。重组蛋白具有活性，最适 pH 为 5.0，最适温度为 37°C。木葡聚糖低聚物的 Km 值为 20.9 mM。PrXTH1 能够与不同的木葡聚糖结构相互作用，但对纤维素作为底物没有活性，在响应倾斜时重塑细胞壁结构。
