Computer graphic study on models of the molybdenum cofactor of xanthine oxidase

Within the scope of our molecular modeling studies on xanthine oxidase (XOD) inhibition by purine analogs we were interested to build up a three-dimensional model of the molybdenum active site. Spectroscopic data indicated that a Mo (VI)atom which is coordinated to sulfur, oxygen and/or nitrogen is clearly involved in substrate binding. In the present study, those data and X-ray crystallography data were used to reconstruct molybdenum-organic complexes from models proposed in the literature. The computer graphic-assisted modeling and evaluation of the model complexes show that the description of the molybdenum center needs further refinement.