ABSTRACT
New catalytic functions of human carbonyl- and aldose reductase in tetrahydrobiopterin biosynthesis are proposed. 6-Pyruvoyl tetrahydropterin, an intermediate in the biosynthesis of tetrahydrobiopterin, was converted to 6-lactoyl tetrahydropterin and 1'-hydroxy-2'-oxopropyl tetrahydropterin by carbonyl reductase under anaerobic condition. 1'-Hydroxy-2'-oxopropyl tetrahydropterin was subsequently metabolized to tetrahydrobiopterin by aldose reductase. Based on these results alternative pathways for the synthesis of tetrahydrobiopterin in patients with genetic defects of sepiapterin reductase are suggested.
Subject(s)
Alcohol Oxidoreductases/metabolism , Aldehyde Reductase/metabolism , Biopterins/analogs & derivatives , Alcohol Oxidoreductases/isolation & purification , Aldehyde Reductase/isolation & purification , Aldo-Keto Reductases , Biopterins/biosynthesis , Brain/enzymology , Chromatography, Gel , Humans , KineticsABSTRACT
The conversion of dihydroneopterin triphosphate in the presence of 6-pyruvoyl tetrahydropterin synthase was followed by 1H-NMR spectroscopy. The interpretation of the spectra of the product is unequivocal: they show formation of a tetrahydropterin system carrying a stereospecifically oriented substituent at the asymmetric C(6) atom. The spectra are compatible with formation of a (3')-CH3 function, and with complete removal of the 1' and 2' hydrogens of dihydroneopterin triphosphate. The fast-atom-bombardment/mass spectrometry study of the same product yields a [M + H]+ ion at m/z 238 compatible with the structure of 6-pyruvoyl tetrahydropterin. The data support the proposed structure of 6-pyruvoyl tetrahydropterin as a key intermediate in the biosynthesis of tetrahydrobiopterin.
Subject(s)
Biopterins/analogs & derivatives , Phosphorus-Oxygen Lyases , Pterins , Alcohol Oxidoreductases/metabolism , Biopterins/biosynthesis , Magnetic Resonance Spectroscopy , Mass Spectrometry , Models, Chemical , Neopterin/analogs & derivatives , Oxidation-Reduction , Pteridines/metabolism , Pterins/analysis , StereoisomerismABSTRACT
6-Pyruvoyl tetrahydropterin reductase has been implicated in the biosynthesis of tetrahydrobiopterin. Using immunochemical and biochemical techniques the purified human liver enzyme was shown to be identical to aldose reductase. This suggests that 6-pyruvoyl tetrahydropterin reductase may play an additional role in the reduction of aldehydes derived from the biogenic amine neuro-transmitters and corticosteroid hormones as well as in the pathogenesis of diabetic complications, as has been postulated for aldose reductase.
Subject(s)
Aldehyde Reductase/metabolism , Antibodies, Monoclonal , Ketone Oxidoreductases/metabolism , Liver/enzymology , Sugar Alcohol Dehydrogenases/metabolism , Aldehyde Reductase/immunology , Animals , Antibodies, Monoclonal/isolation & purification , Blotting, Western , Humans , Immunodiffusion , Ketone Oxidoreductases/immunology , Kinetics , Mice , Mice, Inbred BALB C/immunology , Substrate SpecificityABSTRACT
A low molecular weight protein (approximately 25,000 D) exhibiting a yellow fluorescence emission peaking at approximately 540 nm was isolated from Vibrio fischeri (strain Y-1) and purified to apparent homogeneity. FMN is the chromophore, but it exhibits marked red shifts in both the absorption (lambda max = 380, 460 nm) and the fluorescence emission. When added to purified luciferase from the same strain, which itself catalyzes an emission of blue-green light (lambda max approximately 495 nm), this protein induces a bright yellow luminescence (lambda max approximately 540 nm); this corresponds to the emission of the Y-1 strain in vivo. This yellow bioluminescence emission is thus ascribed to the interaction of these two proteins, and to the excitation of the singlet FMN bound to this fluorescent protein.
