Theoretical studies on pyridoxal 5'-phosphate-dependent transamination of alpha-amino acids
(c) 2008 Wiley Periodicals, Inc.
| Veröffentlicht in: | Journal of computational chemistry. - 1984. - 29(2008), 12 vom: 09. Sept., Seite 1919-29 |
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| Weitere Verfasser: | , , , |
| Format: | Online-Aufsatz |
| Sprache: | English |
| Veröffentlicht: |
2008
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| Zugriff auf das übergeordnete Werk: | Journal of computational chemistry |
| Schlagworte: | Journal Article Research Support, Non-U.S. Gov't Amino Acids Protons Glutamic Acid 3KX376GY7L Pyridoxal Phosphate 5V5IOJ8338 Aspartate Aminotransferases EC 2.6.1.1 |
| Zusammenfassung: | (c) 2008 Wiley Periodicals, Inc. Density functional methods have been applied to investigate the irreversible transamination between glyoxylic acid and pyridoxamine analog and the catalytic mechanism for the critical [1,3] proton transfer step in aspartate aminotransferase (AATase). The results indicate that the catalytic effect of pyridoxal 5'-phosphate (PLP) may be attributed to its ability to stabilize related transition states through structural resonance. Additionally, the PLP hydroxyl group and the carboxylic group of the amino acid can shuttle proton, thereby lowering the barrier. The rate-limiting step is the tautomeric conversion of the aldimine to ketimine by [1,3] proton transfer, with a barrier of 36.3 kcal/mol in water solvent. A quantum chemical model consisting 142 atoms was constructed based on the crystal structure of the native AATase complex with the product L-glutamate. The electron-withdrawing stabilization by various residues, involving Arg386, Tyr225, Asp222, Asn194, and peptide backbone, enhances the carbon acidity of 4'-C of PLP and Calpha of amino acid. The calculations support the proposed proton transfer mechanism in which Lys258 acts as a base to shuttle a proton from the 4'-C of PLP to Calpha of amino acid. The first step (proton transfer from 4'-C to lysine) is shown to be the rate-limiting step. Furthermore, we provided an explanation for the reversibility and specificity of the transamination in AATase |
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| Beschreibung: | Date Completed 11.09.2008 Date Revised 21.11.2013 published: Print Citation Status MEDLINE |
| ISSN: | 1096-987X |
| DOI: | 10.1002/jcc.20958 |