in the patient and subsequently decrease the likelihood of GVHD. In legumes UO is also an essential enzyme in the ureide pathway, where nitrogen fixation occurs in the root nodules of legumes. The fixed nitrogen is converted to metabolites that are transported from the roots throughout the plant to provide the needed nitrogen for amino acid biosynthesis. In legumes, 2 forms of uricase are found: in the roots, the tetrameric form; and, in the uninfected cells of root nodules, a monomeric form, which plays an important role in nitrogen-fixation. See also 2-oxo-4-hydroxy-4-carboxy-5-ureidoimidazoline decarboxylase References EC 1.7.3