@article {241, title = {Role of tautomerism of 2-azaadenine and 2-azahypoxanthine in substrate recognition by xanthine oxidase}, journal = {Journal of computer-aided molecular design}, volume = {11}, year = {1997}, month = {1997/03//}, pages = {153 - 162}, abstract = {The tautomerism of 2-azaadenine and 2-hypoxanthine has been examined in the gas phase and in aqueous solution. The tautomerism in the gas phase has been studied by means of semiempirical and ab initio quantum-mechanical computations, as well as density-functional calculations. The influence of the aqueous solvent on the relative stability between tautomers has been estimated from self-consistent reaction field calculations performed with different high-level continuum models. The results provide a detailed picture of the tautomeric preference for these purine bases. The importance of tautomerism in the substrate recognition by xanthine oxidase is discussed. Finally, the rate of oxidation of 2-azaadenine and 2-hypoxanthine by xanthine oxidase is discussed in terms of the recognition model at the enzyme active site.}, keywords = {Adenine/analogs \& derivatives/chemistry; Binding Sites; Gases; Hypoxanthines/chemistry; Isomerism; Models, Molecular; Molecular Structure; Solutions; Substrate Specificity; Thermodynamics; Water; Xanthine Oxidase/chemistry/metabolism}, author = {Hernandez,B. and M. Orozco and F. J. Luque} }