Gallic acid induced dose dependent inhibition of lysozyme fibrillation

• Published in: International journal of biological macromolecules 2017-10, Vol.103, p.1224-1231
• Main Authors: Konar, Mouli, Bag, Sudipta, Roy, Pritam, Dasgupta, Swagata
• Format: Article
• Language: English
• Subjects: Amyloid fibril; Animals; Dose-Response Relationship, Drug; Gallic acid; Gallic Acid - pharmacology; Hen egg white lysozyme; Hydrogen-Ion Concentration; Muramidase - chemistry; Protein Aggregates - drug effects
• ISSN: 0141-8130; 1879-0003
• DOI: 10.1016/j.ijbiomac.2017.05.158

[Display omitted] •The anti-amyloidogenic potency of gallic acid has been investigated on hen egg white lysozyme at 65°C and pH 7.4 in 30% ethanol.•Gallic acid inhibits the HEWL fibrillation in a dose dependent manner and the highest inhibition occurs at 200μM gallic acid.•Gel electrophoresis and cyclic voltammetry studies suggest that auto-oxidation of gallic acid plays an important role in inhibition.•GA binds near the hydrophobic Trp residues and most likely restricts hydrophobic exposure under the experimental conditions employed.•Met residues are oxidized to polar sulfoxide-modified side chains that prevent aggregation by creating a polar environment around the protein. Amyloidosis is primarily characterized by the deposition of misfolded protein aggregates. Although the natural polyphenols have long been known as effective amyloid inhibitors, the mechanistic details of their inhibitory actions still remain unclear. Our present study explores the inhibition mechanism of polyphenols by studying the anti-amyloidogenic property of gallic acid (GA), the smallest structural unit of tea polyphenols, on hen egg white lysozyme (HEWL) at physiological pH. Using various spectroscopic techniques such as UV-vis, fluorescence, circular dichroism and dynamic light scattering, and microscopic techniques such as TEM and FESEM, it has been shown that GA potentially inhibits the self-aggregation process in a concentration dependent manner. Gel electrophoresis studies suggest that the o-dihydroxy moiety of GA is oxidized into the quinone moiety and H2O2 in the system under the experimental conditions. The quinone binds near the hydrophobic region of HEWL and restricts hydrophobic exposure. Cyclic voltammetry studies reveal that the Met residues of HEWL are oxidized by H2O2 to highly polar sulfoxide-modified side chains. The partially unfolded intermediates formed under the denaturing conditions employed remain in contact with the solvent thus preventing further aggregation.