modulation of circadian rhythms. Class 3 CPD lyases make up a sister group to the plant cryptochromes, which in turn are a sister group to class 1 CPDs. The Cry-DASH group are CPD lyases highly specific for single-stranded DNA. Members include Vibrio cholerae, X1Cry from Xenopus laevis, and AtCry3 from Arabidopsis thaliana. DASH was initially named after Drosophila, Arabidopsis, Synechocystis, and Human, four taxa initially thought to carry this family of lyases. The categorization has since changed. The "Cry" part of their name was due to initial assumptions that they were cryptochromes. Eukaryotic (6-4)DNA photolyases form a group with animal cryptochromes that control circadian rhythms. They are found in diverse species including Drosophila and humans. The cryptochromes have their own detailed grouping. Bacterial 6-4 lyases (), also known as the FeS-BCP group, form their own outgroup relative to all photolyases. The non-class 2 branch of CPDs tend to be grouped into class 1 in some systems such as PRINTS (PR00147). Although the members of the smaller groups are agreed upon, the phylogeny can vary greatly among authors due to differences in methodology, leading to some confusion with authors who try to fit everything (sparing FeS-BCP) into a two-class classification. The cryptochromes form a polyphyletic group including photolyases that have lost their DNA repair activity and instead control circadian rhythms. Application Adding photolyase from a blue-green algae Anacystis nidulans, to HeLa cells partially reduced DNA damage from UVB exposure. Human proteins containing this domain Cryptochromes: CRY1; CRY2 Nomenclature 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). This enzyme belongs to the family of lyases, specifically in the "catch-all" class of carbon-carbon lyases. References Further reading External links EC 4.1.99 DNA repair Enzymes of known structure Flavoproteins