Galactosyl-mimodye ligands for Pseudomonas fluorescens beta-galactose dehydrogenase

Protein molecular modelling and ligand docking were employed for the design of anthraquinone galactosyl-biomimetic dye ligands (galactosyl-mimodyes) for the target enzyme galactose dehydrogenase (GaDH). Using appropriate modelling methodology, a GaDH model was build based on a glucose-fructose oxidoreductase (GFO) protein template. Subsequent computational analysis predicted chimaeric mimodye-ligands comprising a NAD-pseudomimetic moiety (anthraquinone diaminobenzosulfonic acid) and a galactosyl-mimetic moiety (2-amino-2-deoxygalactose or shikimic acid) bearing an aliphatic 'linker' molecule. In addition, the designed mimodye ligands had an appropriate in length and chemical nature 'spacer' molecule via which they can be attached onto a chromatographic support without steric clashes upon interaction with GaDH. Following their synthesis, purification and analysis, the ligands were immobilized to agarose. The respective affinity adsorbents, compared to other conventional adsorbents, were shown to be superior affinity chromatography materials for the target enzyme, Pseudomonas fluorescensbeta-galactose dehydrogenase. In addition, these mimodye affinity adsorbents displayed good selectivity, binding low amounts of enzymes other than GaDH. Further immobilized dye-ligands, comprising different linker and/or spacer molecules, or not having a biomimetic moiety, had inferior chromatographic behavior. Therefore, these new mimodyes suggested by computational analysis, are candidates for application in affinity labeling and structural studies as well as for purification of galactose dehydrogenase.