Biological modeling as a mechanical study of aldehydes oxidation by xantine oxidase enzyme

In the mechanism for purine metabolism the xanthenes oxidase enzyme has physiological importance. According to this hypothesis the xanthenes oxidase enzyme catalyzes the oxidation of xanthine to uric acid which plays a crucial role in gout, facilitate the reduction of oxidizing substrate and important for drug oxidation. Our calculation results indicate that in the catalysis stage the transition state is predicted in well tetrahedral complex formation with the strong bond formation of O_eq-C_CRH and S_Mo-H_RH, and the cleavage of O_CRH-H_RH and Mo-O_eq. This transition state is more reactant like, one imaginary negative frequency is performed and, high activation barriers are often obtained due to the absence of factors that stabilize the accumulation of charge on the substrate at the transition state. In this case the protonated aldehyde substrates more favored for the oxidation reaction with xanthine oxidase in comparison with the corresponding deprotenated aldehydes. And a step wise mechanism is found to be more favored for the oxidation of protonated formaldehyde with a proton coupled electron transfer and intermediate formation in the product bound. The result indicates that the enzyme xanthine oxidase is responsible for the oxidation of aldehydes based on the environment of the active site located. Our mechanistic study of the protonated formaldehyde oxidation provides an understanding in how the reaction path takes place and provides the way to study the catalytic mechanism on different oxidation substrates by xanthine oxidase enzyme.