Faisal Mohammad, Alatar Abdulrahman A, Ahmad Saheem
Department of Biosciences, Integral University, Lucknow, UP, 226026, India.
Department of Botany & Microbiology, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia.
Protein Pept Lett. 2017;24(3):241-244. doi: 10.2174/0929866524666170117142723.
Non-enzymatic glycation is the addition of free carbonyl group of reducing sugar to the free amino groups of proteins and leads to the formation of early glycation products and further into advanced glycation end products (AGEs). Fructose reacts rapidly with the free amino groups of proteins to form AGEs. AGEs are believed to be involved in the pathogenesis of several diseases, particularly in diabetic complications. In this study, IgG was glycated with fructose monosaccharide at 10 mM concentration for varying time interval. The reaction mixture was kept at 37ºC. The early glycation of IgG was done by nitroblue tetrazolium assay (NBT), and the generation of AGEs was done by the extent of side chain modifications (lysine and arginine), Nε-carboxymethyl lysine, pentosidine and carbonyl content. The decrease in free lysine and arginine residues suggests that protein 'IgG' has undergone modification specifically on epsilon amino groups of lysine and arginine. Additionally, their fluorescence and absorbance characteristics were also systematically studied. The results suggest that the maximum Amadori product (ketoamine content) was formed on sixth day of the incubation. The conformational structural perturbation was observed within the glycated IgG protein as studied by using various physicochemical techniques. This study reports structural perturbation, formation of various intermediates and AGEs.
非酶糖基化是指还原糖的游离羰基与蛋白质的游离氨基结合，导致早期糖基化产物的形成，并进一步生成晚期糖基化终末产物（AGEs）。果糖能迅速与蛋白质的游离氨基反应形成AGEs。AGEs被认为与多种疾病的发病机制有关，尤其是糖尿病并发症。在本研究中，将IgG与浓度为10 mM的果糖单糖在不同时间间隔下进行糖基化反应。反应混合物保持在37℃。通过硝基蓝四唑试验（NBT）检测IgG的早期糖基化，通过侧链修饰程度（赖氨酸和精氨酸）、Nε-羧甲基赖氨酸、戊糖苷和羰基含量检测AGEs的生成。游离赖氨酸和精氨酸残基的减少表明蛋白质“IgG”在赖氨酸和精氨酸的ε氨基上发生了特异性修饰。此外，还系统研究了它们的荧光和吸收特性。结果表明，在孵育的第六天形成了最大的Amadori产物（酮胺含量）。通过各种物理化学技术研究发现，糖基化IgG蛋白内部发生了构象结构扰动。本研究报道了结构扰动、各种中间体和AGEs的形成。
