| Autor: |
Bracher, A, Eisenreich, W, Schramek, N, Ritz, H, Götze, E, Herrmann, A, Gütlich, M, Bacher, A |
| Zdroj: |
Journal of Biological Chemistry; October 1998, Vol. 273 Issue: 43 p28132-41, 10p |
| Abstrakt: |
GTP cyclohydrolase I catalyzes a ring expansion affording dihydroneopterin triphosphate from GTP. [1',2',3',4',5'-13C5, 2'-2H1]GTP was prepared enzymatically from [U-13C6]glucose for use as enzyme substrate. Multinuclear NMR experiments showed that the reaction catalyzed by GTP cyclohydrolase I involves the release of a proton from C-2' of GTP that is exchanged with the bulk solvent. Subsequently, a proton is reintroduced stereospecifically from the bulk solvent. This is in line with an Amadori rearrangement mechanism. The proton introduced from solvent occupies the pro-7R position in the enzyme product. The data also confirm that the reaction catalyzed by pyruvoyltetrahydropterin synthase results in the incorporation of solvent protons into positions C-6 and C-3' of the enzyme product. On the other hand, the reaction catalyzed by sepiapterin reductase does not involve any detectable incorporation of solvent protons into tetrahydrobiopterin. |
| Databáze: |
Supplemental Index |
| Externí odkaz: |
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