label: phosphoribosyl-AMP cyclohydrolase activity
label_lc: phosphoribosyl-amp cyclohydrolase activity
description: "Catalysis of the reaction: 1-(5-phosphonatoribosyl)-5'-AMP + H2O = 1-(5-phosphoribosyl)-5-[(5-phosphoribosylamino)methylideneamino]imidazole-4-carboxamide."