PATHWAY: Purine metabolism; IMP biosynthesis via de novo pathway; 5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxamide from 5-amino-1-(5-phospho-D-ribosyl)imidazole-4-carboxylate: step 1/2. {ECO:0000256|ARBA:ARBA00004672, ECO:0000256|HAMAP-Rule:MF_00137}.