Rasburicase (trade names Elitek in the US and Fasturtec in the EU) is a medication that helps to clear uric acid from the blood. It is a recombinant version of urate oxidase, an enzyme that metabolizes uric acid to allantoin. Urate oxidase is known to be present in many mammals but does not naturally occur in humans. Rasburicase is produced by a genetically modified "Saccharomyces cerevisiae" strain. The complementary DNA (cDNA) coding for rasburicase was cloned from a strain of "Aspergillus flavus".