Editing DNA (section)

=== DNA enzymes or catalytic DNA ===
{{further|Deoxyribozyme}}
[[Deoxyribozyme]]s, also called DNAzymes or catalytic DNA, were first discovered in 1994.<ref name="Breaker 223–229">{{cite journal | vauthors = Breaker RR, Joyce GF | title = A DNA enzyme that cleaves RNA | journal = Chemistry & Biology | volume = 1 | issue = 4 | pages = 223–29 | date = December 1994 | pmid = 9383394 | doi = 10.1016/1074-5521(94)90014-0 }}</ref> They are mostly single stranded DNA sequences isolated from a large pool of random DNA sequences through a combinatorial approach called [[in vitro]] selection or [[systematic evolution of ligands by exponential enrichment]] (SELEX). DNAzymes catalyze variety of chemical reactions including RNA-DNA cleavage, RNA-DNA ligation, amino acids phosphorylation-dephosphorylation, carbon-carbon bond formation, etc. DNAzymes can enhance catalytic rate of chemical reactions up to 100,000,000,000-fold over the uncatalyzed reaction.<ref>{{cite journal | vauthors = Chandra M, Sachdeva A, Silverman SK | title = DNA-catalyzed sequence-specific hydrolysis of DNA | journal = Nature Chemical Biology | volume = 5 | issue = 10 | pages = 718–20 | date = October 2009 | pmid = 19684594 | pmc = 2746877 | doi = 10.1038/nchembio.201 }}</ref> The most extensively studied class of DNAzymes is RNA-cleaving types which have been used to detect different metal ions and designing therapeutic agents. Several metal-specific DNAzymes have been reported including the GR-5 DNAzyme (lead-specific),<ref name="Breaker 223–229" /> the CA1-3 DNAzymes (copper-specific),<ref>{{cite journal | vauthors = Carmi N, Shultz LA, Breaker RR | title = In vitro selection of self-cleaving DNAs | journal = Chemistry & Biology | volume = 3 | issue = 12 | pages = 1039–46 | date = December 1996 | pmid = 9000012 | doi = 10.1016/S1074-5521(96)90170-2 | doi-access = free }}</ref> the 39E DNAzyme (uranyl-specific) and the NaA43 DNAzyme (sodium-specific).<ref>{{cite journal | vauthors = Torabi SF, Wu P, McGhee CE, Chen L, Hwang K, Zheng N, Cheng J, Lu Y | title = In vitro selection of a sodium-specific DNAzyme and its application in intracellular sensing | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 112 | issue = 19 | pages = 5903–08 | date = May 2015 | pmid = 25918425 | pmc = 4434688 | doi = 10.1073/pnas.1420361112 | bibcode = 2015PNAS..112.5903T | doi-access = free }}</ref> The NaA43 DNAzyme, which is reported to be more than 10,000-fold selective for sodium over other metal ions, was used to make a real-time sodium sensor in cells.