Oleuropein, a terpene-derived glycosylated secoiridoid biosynthesized exclusively by members of the Oleaceae family, is involved in a two-component defense system comprising a β-glucosidase that activates oleuropein into a toxic glutaraldehyde-like structure. Oleuropein and its deglycosylated derivatives have high pharmaceutical interest. In this study we determined that the in planta heterologous expressed OeGLU, an oleuropein-specific β-glucosidase from olive (Olea europaea), had enzymatic kinetics similar to the olive native enzyme. The C terminus encompassing the nuclear localization signal sequesters the enzyme in the nucleus, and predetermines the protein-protein recognition and homodimerization. Biochemical analysis revealed that OeGLU is a homomultimer with high M r. In silico prediction modeling of the complex structure and bimolecular fluorescence complementation analyses revealed that the C terminus of OeGLU is essential for the proper assembly of an octameric form, a key conformational feature that determines the activity of the enzyme. Our results demonstrate that intrinsic characteristics of the OeGLU ensure separation from oleuropein and keep the dual-partner defensive system conditionally inactive. Upon cell destruction, the dual-partner defense system is activated and olive massively releases the arsenal of defense.
橄榄苦苷是一种萜烯衍
生物,由蔷薇科植物的成员专门合成,参与一种双组分防御系统,该系统由β-
葡萄糖苷酶激活
橄榄苦苷,使其形成有毒的
戊二醛结构。
橄榄苦苷及其脱糖基衍
生物具有很高的药用价值。在这项研究中,我们确定了一种来自橄榄(Olea europaea)的
橄榄苦苷特异性β-
葡萄糖苷酶,即植物异源表达的OeGLU,其酶动力学与橄榄天然酶相似。包含核定位信号的C端将酶隔离在细胞核中,并预先确定蛋白质-蛋白质识别和同源二聚体。
生物化学分析表明,OeGLU是一种具有高M r的同源多聚体。对复杂结构的计算机预测建模和双分子荧光互补分析表明,OeGLU的C端对于八聚体形式的正确组装至关重要,这是决定酶活性的关键构象特征。我们的研究结果表明,OeGLU的固有特性确保其与
橄榄苦苷分离,并使双伴侣防御系统有条件地处于非活动状态。细胞破坏后,双伴侣防御系统被激活,橄榄大量释放防御武器。