INFLUENCE OF NANOPARTICLES ON THERMAL STABILITY OF ASPARTATE AMINOTRANSFERASE

Abstract

For the first time, the complex study of influence of gold, titan dioxide and magnetite nanoparticles on the catalytic properties, thermo-inactivation and aggregation of oligomeric enzyme was performed on the example of aspartate aminotransferase. It has been established that coating of nanoparticles with dextran sulphate contributed to the increase of thermostability of mAspAT, which was observed at 60 0C and higher. The antiaggregation strength of nanoparticles can be ranged as follows: TiO2 NP > Au NPs > Fe3O4 NPs. The aim of the research - comparative study of the kinetic of thermal inactivation of mitochondrial aspartate aminotransferase (mAspAT) in the presence of native and dextran sulfate-modified TiO2 and Fe3O4 nanoparticles (NP). Both, native and dextran sulphate-modified NPs showed the strongest thermal protection at 60 0С and above. The thermal inactivation rate constant (kin) of mAspAT was significantly decreased in the presence of NP-TiO2. Modification of NP surface with dextran sulphate enhanced that effect. Magnetite NP had revealed lower thermal protecting properties. Structural stability of mAspAT in the presence of NPs was characterized by the following thermodynamic parameters: Еаin (inactivation energy), ∆H (enthalpy), and ∆S (entropy) and ∆G (Gibbs free energy). In conclusion, interaction between mAspAT and NPs leads to increase of conformational rigidity of the enzyme and depends mainly on the nature of NP. Stability of gold colloid nanoparticles (Au NPs) is dependent on many factors like buffer concentration and pH values of medium, as well the recombinant AspAT can protect gold colloid nanoparticles from aggregation caused by influence of acidity of buffer or medium