In enzymology, a deoxyribodipyrimidine photo-lyase (EC 4.1.99.3) is an enzyme that catalyzes the chemical reaction cyclobutadipyrimidine (in DNA) ⇌ {\displaystyle \rightleftharpoons } 2 pyrimidine residues (in DNA) Hence, this enzyme has one substrate, cyclobutadipyrimidine (in DNA), and one product, pyrimidine residues (in DNA). This enzyme belongs to the family of lyases, specifically in the "catch-all" class of carbon-carbon lyases. The systematic name of this enzyme class is deoxyribocyclobutadipyrimidine pyrimidine-lyase. Other names in common use include photoreactivating enzyme, DNA photolyase, DNA-photoreactivating enzyme, DNA cyclobutane dipyrimidine photolyase, DNA photolyase, deoxyribonucleic photolyase, deoxyribodipyrimidine photolyase, photolyase, PRE, PhrB photolyase, deoxyribonucleic cyclobutane dipyrimidine photolyase, phr A photolyase, dipyrimidine photolyase (photosensitive), and deoxyribonucleate pyrimidine dimer lyase (photosensitive). It has 2 cofactors: FAD, and 5,10-Methenyltetrahydrofolate.