Urate oxidase without added for the preparation of immunogenic polymer conjugates.

A uricase conjugate comprising a conjugated purified urate oxidase (uricase) with poly (ethylene glycol) or poly (ethylene oxide), wherein said uricase contains tetrameric and octameric purified forms of the uricase preparable by removing aggregates larger than octamers, wherein said uricase contains no more than about 2% of aggregates larger than octamers.