Interaction between Silver Nanoparticles and Two Dehydrogenases: Role of Thiol Groups

Area of Science:

• Nanotechnology
• Biochemistry
• Enzymology

Background:

• Silver nanoparticles (AgNPs) are widely used and interact with biological systems.
• Protein-AgNP interactions are not well understood, impacting biological fluid behavior.
• Enzyme activity can be affected by nanoparticle exposure.

Purpose of the Study:

• To investigate the interaction between AgNPs and two dehydrogenases: glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and malate dehydrogenase (MDH).
• To determine how AgNPs affect enzyme activity and structure.
• To elucidate the role of thiol groups in enzyme sensitivity to AgNPs.

Main Methods:

• Enzyme activity assays were performed on GAPDH and MDH treated with AgNPs and silver ions (Ag+).
• Quantification of free thiols in enzymes after AgNP exposure.
• Circular dichroism (CD) spectroscopy was used to assess changes in enzyme secondary structure.

Main Results:

• AgNPs bind to thiol groups on GAPDH and MDH, reducing available thiols and inhibiting enzyme activity.
• Enzymes were 24-30 times more sensitive to Ag+ than to AgNPs, indicating dissolved Ag+ contributes to inhibition.
• GAPDH, with active site thiols, was more sensitive than MDH, which lacks active site thiols, suggesting thiol location is critical.
• MDH exhibited greater alterations in global secondary structure than GAPDH upon AgNP treatment, as shown by CD spectra.

Conclusions:

• Thiol groups, especially those in the active site, are key determinants of enzyme sensitivity to AgNPs.
• AgNPs can inhibit enzyme function through thiol binding and potentially alter enzyme structure.
• Understanding these interactions is crucial for assessing the biological impact of AgNPs.