Department of Biochemistry, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh, India.
Department of Biochemistry, Aligarh Muslim University, Aligarh 202002, Uttar Pradesh, India.
Int J Biol Macromol. 2019 Jul 15;133:945-956. doi: 10.1016/j.ijbiomac.2019.04.036. Epub 2019 Apr 18.
Abiotic stress induced by heavy metals retards the growth and development of plants. Therefore, it is essential to have an insight into the potential toxic effects of heavy metals. The present article investigates the effect of zinc and cadmium on the structure and function of garlic phytocystatin (GPhyCys). The cysteine proteinase inhibitory assay showed a reduction in the inhibitory activity upon binding with zinc and cadmium. UV-vis absorption spectroscopy revealed the complex formation of zinc and cadmium with garlic phytocystatin. Fluorescence quenching experiment confirmed the quenching of fluorophores upon binding of zinc and cadmium. Synchronous and 3-dimensional fluorescence spectroscopy suggest the alteration in the microenvironment around aromatic residues of garlic phytocystatin upon binding with the above metals. Circular dichroism showed a reduction in the alpha-helical content of native garlic phytocystatin. Scanning electron micrographs showed the morphological changes in the native garlic phytocystatin upon addition of zinc and cadmium. The observations confirmed the alteration in structure and conformation of garlic phytocystatin upon interaction with zinc and cadmium. It can be safely concluded that the high concentration of zinc and cadmium can alter the functioning of cysteine proteinase present in garlic and affects the growth and development of plants.
重金属引起的非生物胁迫会阻碍植物的生长和发育。因此，深入了解重金属的潜在毒性作用至关重要。本文研究了锌和镉对大蒜植物半胱氨酸蛋白酶抑制剂（GPhyCys）结构和功能的影响。半胱氨酸蛋白酶抑制活性测定显示，锌和镉结合后抑制活性降低。紫外-可见吸收光谱显示锌和镉与大蒜植物半胱氨酸蛋白酶抑制剂形成复合物。荧光猝灭实验证实锌和镉结合后荧光团发生猝灭。同步荧光和三维荧光光谱表明，结合上述金属后，大蒜植物半胱氨酸蛋白酶抑制剂中芳香族残基周围的微环境发生改变。圆二色性显示天然大蒜植物半胱氨酸蛋白酶抑制剂的α-螺旋含量降低。扫描电子显微镜观察到加入锌和镉后天然大蒜植物半胱氨酸蛋白酶抑制剂的形态发生变化。这些观察结果证实了锌和镉与大蒜植物半胱氨酸蛋白酶抑制剂相互作用后结构和构象的改变。可以安全地得出结论，高浓度的锌和镉会改变大蒜中存在的半胱氨酸蛋白酶的功能，从而影响植物的生长和发育。
