IUBMB Enzyme Nomenclature


Accepted name: (6-4)DNA photolyase

Reaction: (6-4) photoproduct (in DNA) = 2 pyrimidine residues (in DNA)

For diagram of reaction, click here.

Other name(s): DNA photolyase; H64PRH; NF-10; phr (6-4); PL-(6-4); OtCPF1; (6-4) PHR; At64PHR

Systematic name: (6-4) photoproduct pyrimidine-lyase

Comments: 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: BRENDA, EXPASY, KEGG, Metacyc, PDB, CAS registry number:


1. Hitomi, K., DiTacchio, L., Arvai, A.S., Yamamoto, J., Kim, S.T., Todo, T., Tainer, J.A., Iwai, S., Panda, S. and 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 (2009) 6962-6967. [PMID: 19359474]

2. Schleicher, E., Hitomi, K., Kay, C.W., Getzoff, E.D., Todo, T. and Weber, S. Electron nuclear double resonance differentiates complementary roles for active site histidines in (6-4) photolyase. J. Biol. Chem. 282 (2007) 4738-4747. [PMID: 17164245]

[EC created 2009]

Return to EC 4.1.99 home page
Return to EC 4.3 home page
Return to EC 4 home page
Return to Enzymes home page
Return to IUBMB Biochemical Nomenclature home page