Abstract
Background: Urate oxidase is absent in humans so the enzyme is considered as an important therapeutic agent to control hyperuricemic disorders. Currently available enzymes with pharmaceutical applications have adverse effects associated with allergic reactions and anaphylactic shocks, in case of chronic treatment. Therefore, developing variant forms of the enzyme, with lower immunogenicity and similar or higher activity, is of great importance.
Aim: Here, we tried to improve the structure of a recently resurrected ancestral mammalian urate oxidase (which is claimed to have higher enzymatic activity compared to other mammalian counterparts) by introducing eight rational mutations and verified the consequence of these mutations on immunogenicity, stability and the affinity of protein to uric acid by computational techniques. Methods: After modeling the full-length wild-type and mutant structures, structural dynamics were monitored through 20 ns and 50 ns of molecular dynamics simulation by GROMACS software package for the structures holding and lacking uric acid, respectively. Results: Simulation results implied maintenance of 3D arrangement, volume and compactness between wild-type and mutant structures. However, residues of the mutated structure showed a higher tendency for hydrogen bond formation leading to a more stable and more soluble protein package with a higher surface area buried between protein chains. We also used the DiscoTope-2.0 server to map changes in immunogenicity index of 50 structures derived from the last 10ns of simulation. Conclusion: Finally, this study suggests a urate oxidase mutant with improved overall stability, reduced immunogenicity and slightly lower affinity for uric acid compared to the resurrected ancestral mammalian urate oxidase.Keywords: Molecular dynamics simulation, molecular modeling, urate oxidase, uricase.
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