Bifunctional purine biosynthesis protein PURH is a protein that in humans is encoded by the ATIC gene.
ATIC encodes an enzyme which generates inosine monophosphate from aminoimidazole carboxamide ribonucleotide.
It has two functions:
*  - 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase
*  - IMP cyclohydrolase