Spectroscopic characterisation of interaction of ferulic acid with aldehyde dehydrogenase (ALDH)

- Interaction of Ferulic acid with ALDH was studied at pH 5.0, 7.4 and 9.0.
- Ferulic acid binding to ALDH is purely dynamic quenching mechanism.
- The stoichiometry of ferulic acid-ALDH binding was not perceptive and is 2:1 at saturating ferulic acid concentration.
- The binding cause slight perturbation in the ALDH secondary and tertiary structures and consequently reduced the activity of ALDH.

Interaction of a pharmacological important phenolic, ferulic acid, with Aldehyde dehydrogenase (ALDH) at the simulative pH condition, was studied using spectroscopic approach. Ferulic acid caused a decrease in the fluorescence intensity formed from ALDH-ferulic acid complex resulting in mixed inhibition of ALDH activity (IC50 = 30.65 μM). The intrinsic quenching was dynamic and induced altered conformation of ALDH and made the protein less compact but might not unfold it. ALDH has two binding sites for ferulic acid at saturating concentrations having association constant of 1.35 × 103 L mol−1 and a dissociation constant of 9.7 × 107L mol−1at 25 °C indicating ALDH-ferulic acid complex formation is more favourable than its dissociation. The interaction was not spontaneous and endothermic and suggests the involvement of hydrophobic interactions with a FRET binding distance of 4.49 nm. Change in pH near and far from isoelectric points of ferulic acid did not affect the bonding interaction. Using trehalose as viscosogen, the result from Stoke-Einstein hypothesis showed that ferulic acid-ALDH binding and dissociation equilibrium was diffusion controlled. These results clearly suggest the unique binding properties and lipophilicity influence of ferulic acid.

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