Circular Dichroism and Magnetic Circular Dichroism Spectroscopy of the Catalytically Competent Ferrous Active Site of Phenylalanine Hydroxylase and Its Interaction with Pterin Cofactor
| Autor: | Jyllian N. Kemsley, Kelly Loeb Zaleski, Edward I. Solomon, John P. Caradonna,§ and, Nataša Mitić |
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| Rok vydání: | 1999 |
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| Zdroj: | Journal of the American Chemical Society. 121:1528-1536 |
| ISSN: | 1520-5126 0002-7863 |
| DOI: | 10.1021/ja9833063 |
| Popis: | The tetrahydrobiopterin-dependent enzyme phenylalanine hydroxylase (PAH) contains one non-heme iron atom per subunit that is required for reactivity. We have applied circular dichroism (CD), magnetic circular dichroism (MCD), and variable-temperature, variable-field (VTVH) MCD spectroscopies to investigate the geometric and electronic structure of the catalytically relevant ferrous active site and its interaction with the cofactor analogue 5-deaza-6-methyltetrahydropterin, in the absence and presence of substrate. Excited-state ligand field CD and MCD data indicate that the six-coordinate ferrous active site of the resting and N-ethylmaleimide-activated enzyme is not perturbed by the addition of pterin cofactor in the absence of substrate (Δ5Eg = 1900 cm-1, 10Dq = 9850 cm-1). VTVH MCD analysis yields a ground-state splitting also consistent with an unperturbed six-coordinate ferrous site (Δ5T2g = −285 or −1150 cm-1). Addition of pterin in the presence of l-phenylalanine (l-Phe), however, results in large ... |
| Databáze: | OpenAIRE |
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