GO:0004635

phosphoribosyl-AMP cyclohydrolase activity

GO Category: 
molecular_function
Details: 
Catalysis of the reaction: 1-(5-phosphonatoribosyl)-5'-AMP + H(2)O = 1-(5-phosphoribosyl)-5-[(5-phosphoribosylamino)methylideneamino]imidazole-4-carboxamide.