InterPro domain: IPR014306

Members of this family, hydroxyisourate hydrolase, represent a distinct clade of transthyretin-related proteins. Bacterial members typically are encoded next to ureidoglycolate hydrolase and often near either xanthine dehydrogenase or xanthine/uracil permease genes and have been demonstrated to have hydroxyisourate hydrolase activity [ 1 ]. In eukaryotes, a clade separate from the transthyretins (a family of thyroid-hormone binding proteins) has also been shown to have HIU hydrolase activity in urate catabolizing organisms [ 2 ]. Transthyretin, then, would appear to be the recently diverged paralog of the more ancient HIUH family.

1. Transthyretin-related proteins function to facilitate the hydrolysis of 5-hydroxyisourate, the end product of the uricase reaction. FEBS Lett. 579, 4769-74
2. Mouse transthyretin-related protein is a hydrolase which degrades 5-hydroxyisourate, the end product of the uricase reaction. Mol. Cells 22, 141-5