biostudies-literatureYamada DMEXT | Japan Science and Technology Agency (JST)MEXT | Japan Society for the Promotion of Science (JSPS)256https://www.ebi.ac.uk/biostudies/studies/S-EPMC12397333biostudies-literatureUnknown8(1)Ultraviolet (UV) irradiation of DNA causes genotoxic photolesions, such as carcinogenic pyrimidine(6-4)pyrimidone photoproducts ((6-4)PPs). In many organisms, (6-4)PPs are repaired by (6-4) photolyases, which contain a flavin chromophore and use blue light energy to initiate the catalytic reaction. Although (6-4)PP repair has been shown to require the input of two successive photons, details of the mechanism remain elusive. Here, we applied recently developed time-resolved UV and infrared (IR) spectroscopic techniques to capture a key intermediate that awaits the second photon in the repair reaction of Xenopus laevis (6-4) photolyase. The results indicate that the intermediate is formed within 500 μs following the initial absorption of a photon and contains a four-membered oxetane ring thaCommunications chemistryInfrared and ultraviolet spectroscopic characterization of a key intermediate during DNA repair by (6-4) photolyase.PMC12397333JP19H05784JP22H04751JP20H05442JP24H02263JPMJFR2057Hamamura TYanagisawa SYamada DYamamoto JShigeta YKadono AMaeno TKubo MSato WfalseInfrared and ultraviolet spectroscopic characterization of a key intermediate during DNA repair by (6-4) photolyase.Ultraviolet (UV) irradiation of DNA causes genotoxic photolesions, such as carcinogenic pyrimidine(6-4)pyrimidone photoproducts ((6-4)PPs). In many organisms, (6-4)PPs are repaired by (6-4) photolyases, which contain a flavin chromophore and use blue light energy to initiate the catalytic reaction. Although (6-4)PP repair has been shown to require the input of two successive photons, details of the mechanism remain elusive. Here, we applied recently developed time-resolved UV and infrared (IR) spectroscopic techniques to capture a key intermediate that awaits the second photon in the repair reaction of Xenopus laevis (6-4) photolyase. The results indicate that the intermediate is formed within 500 μs following the initial absorption of a photon and contains a four-membered oxetane ring tha2025-01-01T00:00:00Z2025 Aug2026-07-15T14:15:16.934Z2026-07-05T03:12:31.252ZS-EPMC123973334088359710.1038/s42004-025-01625-9