ABSTRACT
Most oxidoreductases that use NAD+ or NADP+ to transfer electrons in redox reactions display a strong preference for the cofactor. The catalytic efficiency of peach glucitol dehydrogenase (GolDHase) for NAD+ is 1800-fold higher than that for NADP+. Herein, we combined structural and kinetic data to reverse the cofactor specificity of this enzyme. Using site-saturation mutagenesis, we obtained the D216A mutant, which uses both NAD+ and NADP+, although with different catalytic efficiencies (1000 ± 200 and 170 ± 30 M-1 s-1, respectively). This mutant was used as a template to introduce further mutations by site-directed mutagenesis, using information from the fruit fly NADP-dependent GolDHase. The D216A/V217R/D218S triple mutant displayed a 2-fold higher catalytic efficiency with NADP+ than with NAD+. Overall, our results indicate that the triple mutant has the potential to be used for metabolic and cellular engineering and for cofactor recycling in industrial processes.
Subject(s)
Coenzymes/metabolism , L-Iditol 2-Dehydrogenase/metabolism , NADP/metabolism , Plant Proteins/metabolism , Prunus persica/enzymology , Kinetics , L-Iditol 2-Dehydrogenase/chemistry , L-Iditol 2-Dehydrogenase/genetics , Mutagenesis, Site-Directed , Plant Proteins/chemistry , Plant Proteins/geneticsABSTRACT
Glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is considered a classical glycolytic protein that can promote the fusion of phospholipid vesicles and can also play a vital role on in vivo fusogenic events. However, it is not clear how this redox enzyme, which lack conserved structural or sequence motifs related to membrane fusion, catalyze this process. In order to detect if this ability is present in other NAD(P)H dehydrogenases with available structure, spectroscopic studies were performed to evaluate the capability of alcohol dehydrogenase (ADH), glutamic dehydrogenase (GDH) and sorbitol dehydrogenase (SDH) to bind, aggregate, destabilize and fuse vesicles. Based on finite difference Poisson-Boltzmann calculations (FDPB) the protein-membrane interactions were analyzed. A model for the protein-membrane complex in its minimum free energy of interaction was obtained for each protein and the amino acids involved in the binding processes were suggested. A previously undescribed relationship between membrane destabilization and crevices with high electropositive potential on the protein surface was proposed. The putative implication of the non-specific electrostatics on NAD(P)H dehydrogenases induced membrane fusion is discussed.