The IMP cyclohydrolase activity of cytosolic ATIC (bifunctional purine biosynthesis protein PURH) catalyzes the reaction of 5'-phosphoribosyl-5-formaminoimidazole-4-carboxamide (FAICAR) to form inosine 5'-monophosphate and water. The chicken protein has been purified and characterized biochemically (Muellerand Benkovic 1981); structural studies indicate that it occurs as a homodimer (Greasley et al. 2001).
