Amino Acids as Additives against Amorphous Aggregation: In Vitro and In Silico Study on Human Lysozyme.

The effect of 16 amino acids (AA) with various physicochemical properties was investigated on human lysozyme (HL) heat-induced amorphous aggregation. UV-Visible spectrophotometry was used to monitor the kinetics of aggregation in the absence and presence of AA, and transmission electron microscopy (TEM) images were taken from the aggregates. To conduct in silico experiments, Autodock vina was used for docking of AA into protein (via YASARA interface), and FTmap information was checked for an insight onto putative binding sites. Prediction of aggregation-prone regions of lysozyme was made by AGGRESCAN and Tango. Among all tested AA, phenylalanine had the best anti-aggregation effect, followed by lysine. In addition, based on in silico tests, Trp 109 and Val 110 of lysozyme are suggested to be of importance in the aggregation process of the enzyme. In conclusion, phenylalanine, arginine, and lysine were found to affect the nucleation phase of lysozyme aggregation and could be considered as suitable stabilizing structures for this enzyme.