Effect of non-enzymatic glycation on cystatin: a spectroscopic study

The study shows the effect of nonenzymatic glycation on conformation and inhibitory activity of chick pea cystatin (CPC). CPC was incubated with different reducing sugars, pentose (D-Ribose), hexoses (D-Glucose, D-Fructose) at 37 °C for 5 weeks. To evaluate the modification of CPC by these different sugars during the glycation process the extent of the Maillard reaction, conformational, structural and functional changes were investigated. The behaviour of glycated CPC was monitored by the techniques of UV and fluorescence spectroscopies. Specific fluorescence was employed to characterise the glycation and AGEs. The anti-papain activity of glycated CPC was found to be significantly lower as compared to its non-glycated form. Glycation with ribose led to maximum loss in inhibitory activity. It was found that the incubation of CPC with all the mentioned sugars led to a parallel increase in tryptophan fluorescence as well as in Maillard and other AGEs specific fluorescence values and hyperchromicity in the UV-region. Among the sugars studied comparatively ribose was found to be the most active in inducing structural and conformational alterations in the protein suggesting its high reactivity with protein amino groups.