The mechanism of thermal aggregation of glutamate dehydrogenase. The effect of chemical chaperones

Chemical chaperones are low-molecular compounds counteracting protein aggregation. Understanding of the mechanism of their effects is key to their potential use in biotechnology. The aggregation of bovine liver glutamate dehydrogenase (GDH) was studied at 40 degrees C and 50 degrees C using dynamic light scattering, analytical ultracentrifugation, size-exclusion chromatography and differential scanning calorimetry. At 40 degrees C the GDH aggregation proceeds through the slow stages of hexamer dissociation and formation of small oligomeric aggregates. At 50 degrees C these stages are transient. The rate-limiting stage of the overall aggregation process is unfolding of the protein molecule; the order of aggregation with respect to protein, n = 1. The test system based on GDH aggregation at 50 degrees C was used to quantify the antiaggregation activity of chemical chaperones by comparing their half-saturation concentrations [L](0.5). Arginine ethyl ester had the highest anti-aggregation activity, with [L](0.5) = 4 +/- 1 mM. For other additives, [L](0.5) was 22 +/- 1 mM (arginine), 18 +/- 1 mM (argininamide) and 95 +/- 12 mM (proline). Arginine at concentrations up to 300 mM, argininamide at concentrations higher than 300 mM and arginine ethyl ester at concentrations higher than 500 mM enhance aggregate-aggregate sticking. These results explain the mechanism of heat-induced GDH aggregation and its peculiarities at different temperatures or in the presence of chemical chaperones. (c) 2022 Elsevier B.V. and Societe Francaise de Biochimie et Biologie Moleculaire (SFBBM). All rights reserved.

Automated summary

Chemical chaperones are low-molecular compounds that counteract protein aggregation. The aggregation process of bovine liver glutamate dehydrogenase (GDH) at different temperatures was studied, and the unfolding of the protein was found to be the rate-limiting stage of the overall aggregation process. The anti-aggregation activity of chemical chaperones was quantified, and arginine ethyl ester showed the highest activity.