EC - (6-4)DNA photolyase

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IntEnz Enzyme Nomenclature


Accepted name:
(6-4)DNA photolyase
Other names:
DNA photolyase
phr (6-4)
(6-4) PHR
Systematic name:
(6-4) photoproduct pyrimidine-lyase




A flavoprotein (FAD). 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 [2].

Links to other databases

Enzymes and pathways: NC-IUBMB , BRENDA , ExplorEnz , ENZYME@ExPASy , KEGG , MetaCyc , UniPathway
Protein domains and families: PROSITE:PDOC00331
Structural data: CSA , EC2PDB
Gene Ontology: GO:0003914
CAS Registry Number: 37290-70-3


  1. Hitomi, K., DiTacchio, L., Arvai, A. S., Yamamoto, J., Kim, S. T., Todo, T., Tainer, J. A., Iwai, S., Panda, S., Getzoff, E. D.
    Functional motifs in the (6-4) photolyase crystal structure make a comparative framework for DNA repair photolyases and clock cryptochromes.
    Proc. Natl. Acad. Sci. USA 106 : 6962-6967 (2009). [PMID: 19359474]
  2. Schleicher, E., Hitomi, K., Kay, C. W., Getzoff, E. D., Todo, T., Weber, S.
    Electron nuclear double resonance differentiates complementary roles for active site histidines in (6-4) photolyase.
    J. Biol. Chem. 282 : 4738-4747 (2007). [PMID: 17164245]

[EC created 2009]