EC Number   |
Reaction |
Reference |
|---|
   4.1.99.13 | (6-4) photoproduct (in DNA) = 2 pyrimidine residues (in DNA) |
- |
- |
| 4.1.99.13 | (6-4) photoproduct (in DNA) = 2 pyrimidine residues (in DNA) |
A mechanism is proposed in which the histidines residues His 354 and His 358 catalyze the formation of the four-membered ring intermediate in the repair process of this enzyme. When deuterium oxide is used as a solvent, the repair activity is decreased. The proton transfer shown by this isotope effect supports the proposed mechanism |
652092 |
| 4.1.99.13 | (6-4) photoproduct (in DNA) = 2 pyrimidine residues (in DNA) |
Fourier transform infrared spectroscopy is applied to (6-4)DNA photolyase. Differences in FTIR spectra that correspond to (6-4)DNA photolyase photoactivation, substrate binding, and light-dependent DNA repair processes are reported. The presence of DNA carrying a single (6-4) PP uniquely influences vibrations of the protein backbone and a protonated carboxylic acid, whereas photoactivation produces IR spectral changes for the FAD cofactor and the surrounding protein. Difference FTIR spectra for the light-dependent DNA damage repair reaction directly show significant DNA structural changes in the (6-4) lesion and the neighboring phosphate group. Time-dependent illumination of samples with different enzyme:substrate stoichiometries successfully distinguish signals characteristic of structural changes in the protein and the DNA resulting from binding and catalysis |
714245 |
| 4.1.99.13 | (6-4) photoproduct (in DNA) = 2 pyrimidine residues (in DNA) |
in the formation of the (6-4) PPs, a Paterno-Buechi reaction first yields an oxetane-bridged (or azetidine-bridged for cytosine at 3') intermediate. This structure is thermodynamically unstable and rearranges to form a (6-4) PP. During this reaction, the O4' (or N4'H) in the 3' component is transferred to the 5'-component and has thus to be returned to 3' during the repair reaction. Reaction mechanism of repair of (6-4) lesions by (6-4) photolyase, detailed overview. The repair-active redox state of the FAD cofactor is fully reduced FADH- and (6-4) PP-containing substrates are bound in a specific manner. No thermal oxetane formation |
748851 |
| 4.1.99.13 | (6-4) photoproduct (in DNA) = 2 pyrimidine residues (in DNA) |
photoreduction of PhrB differs from the typical pattern because the amino acid of the electron cascade next to FAD is a tyrosine (Tyr391), whereas photolyases and cryptochromes of other groups have a tryptophan as direct electron donor of FAD. Residues Trp342 and Trp390 are essential for charge transfer, Trp342 is located at the periphery of PhrB, while Trp390 connects Trp342 and Tyr391. Charge transfer occurs via the triad 391-390-342. Charge transfer simulations reveal an unusual stabilization of the positive charge on site 391 compared to other photolyases or cryptochromes. Water molecules near Tyr391 offer a polar environment which stabilizes the positive charge on this site, thereby lowering the energetic barrier intrinsic to tyrosine. This opens a second charge transfer channel in addition to tunnelling through the tyrosine barrier, based on hopping and therefore transient oxidation of Tyr391, which enables a fast charge transfer similar to proteins utilizing a tryptophan-triad |
-, 747528 |
| 4.1.99.13 | (6-4) photoproduct (in DNA) = 2 pyrimidine residues (in DNA) |
reaction mechanism of repair of (6-4) lesions by (6-4) photolyase, detailed overview. The repair-active redox state of the FAD cofactor is fully reduced FADH- and (6-4) PP-containing substrates are bound in a specific manner |
748851 |
| 4.1.99.13 | (6-4) photoproduct (in DNA) = 2 pyrimidine residues (in DNA) |
reaction mechanism of repair of (6-4) lesions by (6-4) photolyase, detailed overview. The repair-active redox state of the FAD cofactor is fully reduced FADH- and (6-4) PP-containing substrates are bound in a specific manner. Occurrence of a two-photon mechanism for the repair of a T(6-4)T lesion by the (6-4) PL of Xenopus laevis |
748851 |
| 4.1.99.13 | (6-4) photoproduct (in DNA) = 2 pyrimidine residues (in DNA) |
repair of Dewar valence isomers by (6-4) photolyases involves the rearrangement of the Dewar lesions into the corresponding (6-4) lesions. This reaction requires electron injection. (6-4) photolyases have two catalytic functions: Splitting (6-4) lesions and catalyzing the formal 4pi sigmatropic rearrangement of Dewar isomers to (6-4) lesions |
715278 |
| 4.1.99.13 | (6-4) photoproduct (in DNA) = 2 pyrimidine residues (in DNA) |
repair photocycle of (6-4) thymine photoproduct by (6-4) photolyase, which involves light absorption by the 8-HDF cofactor and transfer of the excitation energy to the FADH-. Intermolecular Coulombic decay resulting in an electron transfer from FADH? to the dimer initiating the splitting process, mechanism, detailed overview. The mechanism requires the C5-OH transfer from C5 of the 5' thymine to the C4' of the 3' thymine followed by H transfer to the N3' of the 3' thymine. Of two conserved histidine residues, only His365 is protonated |
728194 |
| 4.1.99.13 | (6-4) photoproduct (in DNA) = 2 pyrimidine residues (in DNA) |
The overall repair reaction consists of two distinct steps, one of which is light-independent and the other one light-dependent. In the initial light-independent step, a 6-iminium ion is thought to be generated via proton transfer induced by two histidines highly conserved among the (6-4) photolyases.This intermediate spontaneously rearranges to form an oxetane intermediate by intramolecular nucleophilic attack. In the subsequent light-driven reaction, one electron is believed to be transferred from the fully reduced FAD cofactor (FADH-) to the oxetane intermediate thus forming a neutral FADH radical and an anionic oxetane radical, which spontaneously fractures. The excess electron is then back-transferred to the flavin radical restoring the fully reduced flavin cofactor and a pair of pyrimidine bases |
679920, 680604, 680605, 680868, 682048, 682049, 682086, 682153, 682154, 682195, 682198, 682264, 682329, 682855 |
