A modified uricase is described herein, as well as a method of reducing a level of uric acid by contacting a medium with the modified uricase. The modified uricase comprises a uricase polypeptide crosslinked by at least one bifunctional linking moiety that comprises a poly(alkylene glycol) moiety. A molecular weight of the bifunctional linking moiety is from about 1.5 kDa to about 4 kDa, and/or the modified uricase comprises a plurality of polypeptides having the amino acid sequence SEQ ID NO: 2. Further described is a polypeptide having the amino acid sequence SEQ ID NO: 2. A process of preparing the modified uricase is also described, comprising contacting the polypeptide with a crosslinking agent that comprises a poly(alkylene glycol) moiety and at least two aldehyde groups, to obtain a conjugate; and contacting the conjugate with a reducing agent.