title: [Purification and properties of GTP-cyclohydrolase of the yeast Pichia guilliermondii].
abstract: GTP-cyclohydrolase was isolated from the Fe-deficient cells of Pichia guilliermondii and purified 440-fold by treatment of extracts with streptomycin sulfate as well as by protein fractionation with (NH4)2SO4 at 25-45% saturation, gel filtration through Sephadex G-200 and DEAE-cellulose chromatography. The curves for the dependence of specific activity of GTP-cyclohydrolase on substrate and cofactor concentrations are non-hyperbolic; the values of [S]0.5 for GTP and Mg2+ are 2.2 X 10(-5) and 2 X 10(-4) M, respectively. The enzyme activity is inhibited by pyrophosphate ([I]0.5 = 5.8 X 10(-4) M), orthophosphate ([I]0.5 = 4.5 X 10(-3) M), heavy metal ions and chelating agents. The temperature optimum for the enzyme activity lies at 42-45 degrees C. The enzyme is labile at 4 degrees C but can well be stored at -15 degrees C. The pyrimidine product of the cyclohydrolase reaction, 2.5-diamino-6-oxy-4-ribosyl-aminopyrimidine-5'-phosphate, as well as pyrophosphate were purified from the reaction medium and identified.
mesh_terms: D000619:Aminohydrolases / Q000302:isolation & purification*; D001203:Ascomycota / Q000201:enzymology*; D002413:Cations, Divalent; D006136:GTP Cyclohydrolase / Q000302:isolation & purification* / Q000378:metabolism; D007700:Kinetics; D010843:Pichia / Q000201:enzymology*; D013696:Temperature
chemical_list: D002413:Cations, Divalent; D000619:Aminohydrolases; D006136:GTP Cyclohydrolase
vernacular_title: Ochistka i svoĭstva GTP-tsiklogidrolazy drozhzheĭ Pichia guilliermondii.