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