Fatima Aiman, Husain Qayyum
Department of Biochemistry, Faculty of Life Sciences, Aligarh Muslim University, Aligarh 202 002, UP, India.
Int J Biol Macromol. 2007 Jun 1;41(1):56-63. doi: 10.1016/j.ijbiomac.2006.12.007. Epub 2007 Jan 21.
The possible role of carbohydrate moieties in the stabilization of proteins has been investigated by using bitter gourd peroxidase as a model system. A comparative study of glycosylated and non-glycosylated isoenzymes of bitter gourd peroxidase was performed at various temperatures, pH, water-miscible organic solvents, detergents and chaotropic agent like urea. The pH-optima and temperature-optima of both glycosylated and non-glycosylated isoforms of bitter gourd peroxidase remained unchanged. The probes employed were changes in the enzyme activity and fluorescence. The glycosylated form of peroxidase retained greater fraction of enzyme activity against the exposure caused by various physical and chemical denaturants. The unfolding of both forms of enzyme in the presence of high urea concentrations, studied by fluorescence, indicated greater perturbations in the conformation of non-glycosylated preparation. The different properties examined thus indicated that glycosylation plays an important role in the stabilization of native conformation of proteins against the inactivation caused by various types of denaturants.
以苦瓜过氧化物酶作为模型系统，研究了碳水化合物部分在蛋白质稳定化中的可能作用。在不同温度、pH值、与水混溶的有机溶剂、洗涤剂以及诸如尿素等离液剂条件下，对苦瓜过氧化物酶的糖基化和非糖基化同工酶进行了比较研究。苦瓜过氧化物酶糖基化和非糖基化同工型的最适pH值和最适温度均保持不变。所采用的指标是酶活性和荧光的变化。在各种物理和化学变性剂作用下，过氧化物酶的糖基化形式保留了更大比例的酶活性。通过荧光研究在高浓度尿素存在下两种形式酶的解折叠情况，结果表明非糖基化制剂的构象受到更大干扰。因此，所检测的不同性质表明，糖基化在稳定蛋白质天然构象以抵抗各种类型变性剂导致的失活方面起着重要作用。
