Catalyzes the conversion of GTP to 2,5-diamino-6- ribosylamino-4(3H)-pyrimidinone 5'-phosphate (DARP), formate and pyrophosphate (By similarity). 205 PA14_11510 ribA RIBA_PSEAB GTP cyclohydrolase-2 MSVVFVAASKLPTPFGEFTMHGFLDEESGKEHVALSMGDIADGAPVLGRLHSECLTGDALFSLRCDCGFQLEGALAAIAEEGRGVLLYLRQEGRGIGLLNKIRAYELQDGGADTVEANLQLGFGADQRDYAMCQPMLAHLGVSSLRLMTNNPRKVKALESYAITVAERVPLQRGLNKHNRRYLATKAGKLGHMLGSLHQGEAETT GTP cyclohydrolase II