title: Biosynthesis of tetrahydrobiopterin. Purification and characterization of 6-pyruvoyl-tetrahydropterin synthase from human liver.
abstract: 6-Pyruvoyl-tetrahydropterin synthase, which catalyzes the first step in the conversion of 7,8-dihydroneopterin triphosphate to tetrahydrobiopterin, was purified approximately 140,000-fold to apparent homogeneity from human liver. The molecular mass of the enzyme is estimated to be 83 kDa. 7,8-Dihydroneopterin triphosphate was a substrate of the enzyme in the presence of Mg2+, and the pH optimum of the reaction was 7.5 in Tris HCl buffer. The Km value for 7,8-dihydroneopterin triphosphate was 10 microM. The product of this enzymatic reaction was the presumed intermediate 6-pyruvoyl-tetrahydropterin. This latter compound was converted to tetrahydrobiopterin in the presence of NADPH and partially purified sepiapterin reductase from human liver. The conditions and the effect of N-acetylserotonin on this reaction, and on the formation of the intermediates 6-(1'-hydroxy-2'-oxopropyl)-tetrahydropterin and 6-(1' oxo-2'-hydroxypropyl)-tetrahydropterin have been studied.
mesh_terms: D000429:Alcohol Oxidoreductases / Q000302:isolation & purification* / Q000378:metabolism; D001708:Biopterins / Q000031:analogs & derivatives* / Q000096:biosynthesis; D002851:Chromatography, High Pressure Liquid; D006801:Humans; D006863:Hydrogen-Ion Concentration; D008099:Liver / Q000201:enzymology*; D008970:Molecular Weight; D019761:Phosphorus-Oxygen Lyases
chemical_list: D001708:Biopterins; D000429:Alcohol Oxidoreductases; D019761:Phosphorus-Oxygen Lyases; C043497:6-pyruvoyltetrahydropterin synthase; C003402:sapropterin