ATIC protein, also known as 5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase/IMP cyclohydrolase, is a bifunctional enzyme that catalyzes the last two steps in the de novo purine biosynthetic pathway. The N-terminal domain of ATIC possesses phosphoribosylaminoimidazolecarboxamide formyltransferase activity, while the C-terminal domain has IMP cyclohydrolase activity . Mutations in the ATIC gene can lead to AICA-ribosiduria, a condition characterized by the accumulation of AICA riboside and its derivatives in the body.