Glycation of human serum albumin affects its binding affinity towards (−)-epigallocatechin gallate

Abstract

Reducing sugars can modify protein structures in vivo via non-enzymatic methods were identified in different cases of diabetes and glycemia. The synthesis and characterization of glycated analogue of human serum albumin (HSA) has been reported recently by our group (Singha Roy et al. in J Biomol Struct Dyn 2015. doi: 10.1080/07391102.2015.1094749 ). The current paper is focused on the interaction of (−)-epigallocatechin gallate (EGCG), a major green tea component with the glycated HSA. The interaction of EGCG with the glycated HSA has been carried out using steady-state fluorescence and circular dichroism experiments. The quenching constants (k q ) were found in the order of 1013 M−1 s−1, indicating the presence of static quenching mode in the interaction. The binding constants of EGCG–HSA complex was found to be decreased from 7.63 × 104 (Maiti et al. in Proteins Struct Funct Bioinform 64:355–362, 2006) to 3.27 × 104 M−1 at 293 K after glycation of HSA. The changes in entropy (∆S°) of the interaction of EGCG has been altered from +16.23 (with native HSA) to +34.84 J/K mol (with glycated HSA) which may offer a stabilization in α-helix of the glycated HSA during binding. EGCG has shown its affinity to the site 1 (subdomain IIA) of the glycated HSA. Energy transfer parameters revealed the possibility of non-radiative energy transfer from donor Trp 214 to acceptor EGCG.