Developing Functional Mimics of Active Sites of Metalloenzymes Involved in Carbohydrate Binding and Transformation

Carbohydrates comprise the most abundant class of organic molecules in the biosphere and find crucial roles in a vast number of biological functions. Despite their overwhelming importance, the study of metalloenzymes involved in carbohydrate metabolism such as Xylose/Glucose isomerase (XGI) using synthetic models remains largely unexplored.

Towards the goal of expanding the scientific knowledge surrounding the interaction and reactivity of carbohydrates with metal complexes, new biologically relevant transition metal complexes as carbohydrate binding models have been synthesized and fully characterized using several techniques including single crystal X-ray crystallography. Several new ligands were developed to provide a coordination environment around the metal centers very similar to those found in the active site of metalloenzymes. Nearly all of the metal complexes of these new ligands were found to be soluble in common polar solvents including water. The binding of substrates such as D-mannose, D-glucose, D-xylose and xylitol with the water-soluble complexes in different reaction conditions were investigated. The metal complexes showed coordination ability towards the applied substrates. Even in the presence of stoichiometric excess of the substrates, the complexes form only 1:1 (complex/substrate) molar ratio species in solution. Apparent binding constants, pK_app, values between the complexes and the substrates were determined and specific mode of substrate binding has been proposed. Syntheses, characterizations and detailed substrate binding study using spectroscopic techniques and single crystal X-ray diffraction are reported.