Abstract:
Aldehyde dehydrogenase (ALDH) is a superfamily of phase I oxidizing enzyme responsible
for detoxification of biogenic and xenogenic aldehydes to the corresponding carboxylic acids
by means of an NAD(P)+dependent reaction. The enzyme has been implicated in the
protection of prokaryotic and eukaryotic organisms against various stress conditions. ALDH
is also involved in non-enzymatic ligand binding to endobiotics and xenobiotics.Kolaviron, a
biflavonoid, isolated from Garcinia kola (Bitter kola) molecular interaction with ALDH was
investigated by steady state fluorescence and UV-Visible spectroscopies techniques under
physiological conditions.Fluorescence spectra and data showed that kolaviron has a strong
ability to quench the intrinsic fluorescence of ALDH through a mixture of static dynamic
quenching procedure, and the effective quenching constant (Ksv) was 2.57x104 L. mol-1. The
Scatchard plot indicated that Aldehyde dehydrogenase has onebinding sites for kolaviron with
a binding constant (Ka) of 6.4x103 L.mol-1and a dissociation constant of 3.28x10-4L.mol-1 at
298K and pH 7.4 showing a strong bonding interaction of ALDH-kolaviron. The
thermodynamic data suggest that kolaviron binding to ALDH was not spontaneous.
Hydrophobic bondplayed a major role in the bindingat the pH of 7.4 and 5.0, and Van der
Waal bond at the pH of 9.0. UV-Visible spectra of the ALDH-kolaviron complex showed
unperturbed secondary structure but perturbed tertiary structure of ALDH by the ligand.
There was no entropy-enthalpy compensation of ALDH-kolaviron interaction. The
synchronous fluorescence of ALDH-Kolaviron indicated conformational change near the
Tryptophan residue micro-environment rather than tyrosine.According to Forster
non-radiation energy transfer theory, the binding of kolaviron to ALDH was of great
probability of less than 8 nm. This work established a clear relationship between kolaviron
and ALDH and has helped in understanding of the ligand binding properties of the enzyme
and the dynamics and thermodynamics of their interactions.
