Photolyases
| Photolyase | ||
|---|---|---|
|
||
| Crystal structure | ||
| Enzyme classification | ||
| EC, category | 4.1.99.3 , oxidoreductases | |
| Response type | Redox reaction | |
| Substrate | CPD or (6-4) photo product in DNA | |
| Products | native DNA | |
Photolyases are enzymes that help repair DNA . They manage the dissolution of cyclobutane pyrimidine dimers (CPD) and (6-4) photo products , which are formed when the DNA is exposed to ultraviolet radiation .
Occurrence
Photolyases have been found in prokaryotes , eukaryotes and archaea . Functional variants of these proteins are lacking in higher mammals , including humans, whereas they have been detected in marsupials such as the domestic shrew rat ( Monodelphis domestica ) or the rabbit kangaroo Potorous didactylus .
structure
The Escherichia coli photolyase has a molar mass of 54 kDa . The primary cofactor in all photolyases is the redox-active flavin adenine dinucleotide . They also have an antenna complex, either from the pterin - cofactor MTHF (methylenetetrahydrofolate) or deazaflavin cofactor 8-HDF (8-hydroxy-5-Desazariboflavin) consists.
function
Photolyases bind in their active center, depending on the photolyase class, either to CPDs or (6-4) photo products in the DNA. The antenna complex is stimulated by blue or ultraviolet exposure and transfers this stimulation to the reduced redox cofactor (FADH - ). An electron jumps from this to the DNA damage in the active center, which then dissolves. The flavin is then returned to its reduced state by electron transfer from a tryptophan on the enzyme surface. In contrast to other repair mechanisms, the correction takes place without cutting the DNA.
Individual evidence
- ↑ T. Kato, T. Todo, H. Ayaki, K. Ishizaki, T. Morita, S. Mitra, M. Ikenaga: Cloning of a marsupial DNA photolyase gene and the lack of related nucleotide sequences in placental mammals. In: Nucleic acids research. Volume 22, Number 20, October 1994, pp. 4119-4124, PMID 7937136 , PMC 331898 (free full text).
- ↑ A. Yasui, AP Eker, S. Yasuhira, H. Yajima, T. Kobayashi, M. Takao, A. Oikawa: A new class of DNA photolyases present in various organisms including aplacental mammals. In: The EMBO journal. Volume 13, Number 24, December 1994, pp. 6143-6151, PMID 7813451 , PMC 395594 (free full text).