Thermal disaggregation of type B yeast hexokinase by indole derivatives: a mechanistic study

Protein aggregation is a pathological hallmark of several human disorders, and a central problem in biotechnology, occurring during purification, sterilization, shipping and storage of protein structures. The process is a very complex one, characterized with a remarkable polymorphism of aggregates, including soluble amyloid oligomers, amyloid fibrils and amorphous species. While amyloid structure formation has been extensively investigated during the recent years, amorphous aggregation is still not well characterized. Use of small molecules that affect this process could be informative in this regard. In order to explore the inhibiting effect of small molecules on the amorphous aggregate formation, yeast hexokinase-B, a key enzyme in metabolism, has been chosen for the present study. Thermal aggregation of the enzyme was investigated in 50 mM phosphate buffer, pH 7 at 55°C and the extent of aggregation was measured by monitoring the increase in absorbance at 350 nm versus time. Possible anti-aggregation effects of a variety of non-specific ligands including indole, tryptophan, carbinol, and indomethacin were explored. Turbidity of the protein solutions was found to be diminished by the presence of these small molecules in the above conditions, with the highest effects being exerted by indomethacin. Dynamic light scattering and HPLC confirmed that indomethacin had the highest anti-aggregation effect. These observations, taken together, suggest that the indole ring is likely to play an important role in aggregation inhibition.