Purification of 6-pyruvoyl Tetrahydropterin 2'-keto Reductase from Human Liver
نویسنده
چکیده
The first reaction is the conversion of GTP to dihydroneopterin triphos phate (NH2TP) catalyzed by a single enzyme, GTP cyclohydrolase (GTPCH) (7). The nature of the next step, a critical one since it is prob ably rate-limiting in man, has long remained unclear due to the high insta bility of the product and the resulting problems of structure elucidation. This key intermediate is 6-pyruvoyl tetrahydropterin (PPH4) whose structure has by now been well defined using NMR and MS (8,9), as well as other tech niques (10,11,12). The elimination of triphosphate and the intramolecular rea rrangement are ca ta 1yzed by one si ngl e enzyme, 6-pyruvoyl tetra hydro pterin synthase (PPH4S), which was purified to homogeneity by Takikawa et al. (13,14). The enzymes which cata1yze the two-step reduction of PPH4 to BH4 are sepi apteri n reductase (SR) and 6-pyruvoyl tetrahydropteri n reduc -
منابع مشابه
Purification and Partial Characterization of 6-pyruvoyl- Tetrahydropterin Reductase from Human Liver
Reduction of 6-pyruvoyl tetrahydropterin (PPH4) during biosynthesis of BH4 can be accomplished by two distinctly different enzymes requiring NADPH. One is sepiapterin reductase (SR) which catalyzes the reduction of both keto functions in the side chain of PPH4 (4,9,12). However, it seems as if the l'-keto function is preferentially reduced since 6-lactoyl tetrahydropterin was never observed to ...
متن کاملBiosynthesis of tetrahydrobiopterin. Purification and characterization of 6-pyruvoyl-tetrahydropterin synthase from human liver.
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...
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Tetrahydrobiopterin (BH(4)) is a cofactor for aromatic amino acid hydroxylases and nitric oxide synthase. The biosynthesis includes two reduction steps catalyzed by sepiapterin reductase. An intermediate, 6-pyruvoyltetrahydropterin (PPH(4)) is reduced to 1(')-oxo-2(')-hydroxypropyl-tetrahydropterin (1(')-OXPH(4)) or 1(')-hydroxy-2(')-oxopropyl-tetrahydropterin (2(')-OXPH(4)), which is further c...
متن کاملTetrahydrobiopterin biosynthesis. Studies with specifically labeled (2H)NAD(P)H and 2H2O and of the enzymes involved.
The biosynthesis of tetrahydrobiopterin from either dihydroneopterin triphosphate, sepiapterin, dihydrosepiapterin or dihydrobiopterin was investigated using extracts from human liver, dihydrofolate reductase and purified sepiapterin reductase from human liver and rat erythrocytes. The incorporation of hydrogen in tetrahydrobiopterin was studied in either 2H2O or in H2O using unlabeled NAD(P)H ...
متن کاملPurification of 6-pyruvoyl-tetrahydropterin synthase from human liver.
The enzyme which catalyzes the first step in the conversion of dihydroneopterin triphosphate to tetrahydrobiopterin has been purified approx. 40,000-fold from human liver to apparent homogeneity. The enzyme has a native molecular weight of approximately 83,000 and consists of four identical subunits, each of which has a molecular weight of approximately 19,000. It contains carbohydrates and is ...
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