Activation of yeast alcohol dehydrogenase in the presence of citrate stabilized gold nanoparticles: An insight into its interaction and modulation mechanism

The presence of nanoparticles in the reaction mixture greatly affects the properties of the bio-macromolecules. Citrate, used as a stabilizing and functionalizing agent assists in forming monodispersed spherical gold nanoparticles (AuNPs). Here, an insight into the role of enzyme:cit-AuNPs ratio in modulating the activity of yeast alcohol dehydrogenase (YADH) is provided in relation with the different levels of agglomerations between cit-AuNPs and YADH. Cit-AuNPs formed were characterized by UV–visible spectrophotometer, transmission electron microscope (TEM), zetasizer, dynamic light scattering (DLS) and energy dispersive x-ray analysis (EDAX). The interaction of YADH with cit-AuNPs was further investigated by absorption, fluorescence and molecular docking analysis, and by using unmodified and thiol-modified YADH. Stable monodispersed cit-AuNPs of size ~10 nm and hydrodynamic radii of 21.2 nm were formed which agglomerated in the presence of higher concentration of YADH. Cit-AuNPs bind to YADH and the activity of the enzyme in their presence depends on the ratio of the enzyme to cit-AuNPs. YADH to cit-AuNPs ratio of 1:5 enhances the activity of the enzyme by 3.1 fold. The nanoparticles are also able to activate YADH in the presence of organic solvents. Thiols of YADH are mainly responsible for the attachment to cit-AuNPs. This provides a different approach of studying industrial, diagnostic and therapeutic applications as well as interactions of bio-macromolecules with nanomaterials.