(GenBank) High confidence in function and specificity; GTP cyclohydrolase I (YP_062947.1| GTP cyclohydrolase I [Leifsonia xyli subsp. xyli str. CTCB07]; NP_870186.1| GTP cyclohydrolase I [Pirellula sp. 1]). catalytic activity: gtp + 2 h(2)o = formate + 2-amino-4-hydroxy-6-(erythro-1,2, 3-trihydroxypropyl)dihydropteridine triphosphate. pathway: tetrahydrofolate biosynthesis; first step. pfam01227,GTP_cyclohydroI, GTP cyclohydrolase I. folE: GTP cyclohydrolase I