title: Occurrence of GTP cyclohydrolase I in Bacillus stearothermophilus.
abstract: A GTP cyclohydrolase which catalyzes the removal of carbon 8 of GTP as formic acid to yield a single pteridine compound occurs in an obligate thermophile Bacillus stearothermophilus ATCC 8005. The enzyme was purified 5.5-fold. Its molecular weight and Stoke's radius were estimated as 105,000 and 45.3 A, respectively. The Km for GTP was 0.98 microM. The temperature and pH optima for activity were 60-65 degrees C and 8.0-8.4, respectively. No divalent cation was required for the reaction. The pteridine product was 3'-triphosphate of 2-amino-4-hydroxy-6-(D-erythro-1',2',3'-trihydroxypropyl)-7,8-dihydropteridine (dihydroneopterin triphosphate), identified by isolating its immediate derivative, 2',3'-cyclic phosphate of 2-amino-4-hydroxy-6-(D-erythro-1',2',3'-trihydroxypropyl)pteridine (neopterin cyclic phosphate). The radioactive product from [8-14C]GTP agreed with 14C-formate. Molar ratio of formate release to pteridine formation was 1.0.
mesh_terms: D000619:Aminohydrolases / Q000378:metabolism*; D006136:GTP Cyclohydrolase / Q000302:isolation & purification / Q000378:metabolism*; D001411:Geobacillus stearothermophilus / Q000201:enzymology*; D007700:Kinetics; D008970:Molecular Weight; D011487:Protein Conformation; D011621:Pteridines / Q000302:isolation & purification
chemical_list: D011621:Pteridines; D000619:Aminohydrolases; D006136:GTP Cyclohydrolase