ADEJOKE N. KOLAWOLE#, L.O. ALADEGBOYE, A.O. AYODEJI
Department of Biochemistry, The Federal University of Technology, P.M.B. 704, Akure, Nigeria
Aldehyde dehydrogenase (ALDH) is a superfamily of phase I oxidizing enzymes 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 oxidative stress conditions. In this study, we investigated into the preferred coenzyme used by the enzyme in carrying out its function at different solution pH and The binding properties of NAD+ and NADP+, rutin, tannic acid, quercetin and gallic acid to aldehyde dehydrogenase was investigated at 25 oC (298 K) and pH 9.0 by UV-Vis absorption spectroscopy and fluorescence quenching spectroscopy. The specific binding constants of NAD+ and NADP+ to the enzyme are 1.50 × 105 M−1 and 1.58 × 105 M−1, respectively. This demonstrates ALDH preference for NADP+, though dual specificity cannot be ruled out; however, the dissociation of the coenzymes from the enzyme was pH dependent. The fluorescence spectra of the interaction of rutin, gallic acid and quercetin with ALDH showed static quenching mechanism while gallic acid was dynamic quenching. All with stoichiometric ratio of one to ALDH. Gallic has the least quenching efficiency. The dissociation of NAD+ from ALDH was also found to be dependent on the viscosity of the solution using glycerol as micro-viscogen and ficcol 400 as macro-viscogen.
Key words: Spectroscopic techniques, aldehyde dehydrogenase, coenzymes, NAD(P)+, ligands
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