5-Aminoimidazole-4-Carboxamide Ribonucleotide Formyltransferase (ATIC)

AICARFT (5-aminoimidazole-4-carboxamide ribonucleotide formyltransferase; EC 2.1.2.3) and IMPCHase (IMP cyclohydrolase; EC 3.5.4.10) catalyze the penultimate and final steps, respectively, of the de novo purine biosynthetic pathway. Both enzymatic activities are present in the same protein, designated ATIC, in all species of prokaryotes and eukaryotes studied by Rayl et al. (1996). The human ATIC cDNA encodes a deduced 591-amino acid protein that is 81% identical to the chicken sequence. Rayl et al. (1996) created truncation mutants of the cDNA and measured their enzymatic properties. In this way they were able to localize the AICARFT activity within the amino-terminal 223 amino acids and the IMPCHase activity to the carboxyl-terminal 406 residues.