Bio-conjugation of Bacillus Fastidiosus-Uricase with methoxy polyethylene glycol derivative and study of physiochemical properties

Abstract

Uricase (EC 1.7.3.3, UC) is an enzyme belonging to the class of oxidoreductases and catalyses the oxidation of uric acid to allantoin, carbon dioxide and hydrogen peroxide. In this present work, Uricase from Bacillus fastidisous was conjugated with methoxypolyethyleneglycol p-nitrophenyl carbonate (mPEG-np) a polyethylene glycol derivative, in order to improve the pharmaceutical properties of therapeutic enzyme uricase. The PEGylated conjugates (uricase-mPEG-np) were synthesized using various ratios of uricase and mPEG-np to get maximum residual activity. The PEGylated uricase showed maximum residual uricolytic activity of 90.9% compared to the unmodified uricase, which was achieved at a ratio of 1:17 of uricase to mPEG-np. PEGylated uricase was further characterized using SDS-PAGE to determine its final molecular weight and approximate number of mPEG molecules attached. The result showed that the molecular weight was increased to 79.4 KDa and the number of mPEG molecules bound per subunit of uricase was approximately 9. Stability of the PEGylated uricase at various temperature and pH was studied and found to be 32 C and pH of 9.0. Further the mechanism of binding and possible sites of binding were studied using molecular modeling and docking software tool ArgusLab 4.0.1 and the two-dimensional image of docked uricase were generated.