Editing RNA world (section)

==== Cofactors ====
:Protein enzymes catalyze various chemical reactions, but over half of them incorporate cofactors to facilitate and diversify their catalytic activities.<ref>{{Cite journal |last=Decker |first=Karl |date=2006-01-17 |title=The Pyridine Nucleotide Coenzymes. Herausgegeben von J. Everse, B. Anderson und K.-S. You. Academic Press, New York 1982. XXXV, 389 S., geb. $ 46.00 |url=http://dx.doi.org/10.1002/ange.19830951241 |journal=Angewandte Chemie |volume=95 |issue=12 |pages=1033–1034 |doi=10.1002/ange.19830951241 |issn=0044-8249}}</ref> Cofactors are essential in biology, as they are based largely on nucleotides rather than amino acids. Ribozymes use nucleotide cofactors to create metabolism, with two basic choices: non-covalent binding or covalent attachment. Both approaches have been demonstrated using directed evolution to reinvent RNA dupes of protein-catalyzed processes. Lorsch and Szostak <ref>{{Cite journal |last1=Ekland |first1=Eric H. |last2=Szostak |first2=Jack W. |last3=Bartel |first3=David P. |date=1995-07-21 |title=Structurally Complex and Highly Active RNA Ligases Derived from Random RNA Sequences |url=http://dx.doi.org/10.1126/science.7618102 |journal=Science |volume=269 |issue=5222 |pages=364–370 |doi=10.1126/science.7618102 |pmid=7618102 |bibcode=1995Sci...269..364E |s2cid=40795082 |issn=0036-8075}}</ref> investigated ribozymes that could phosphorylate themselves and use [[Adenosine triphosphate#ATP analogues|ATP-γS]] as a substrate. However, only one of the seven classes of selected ribozymes had detectable ATP affinity, indicating that the ability to bind ATP was compromised. NAD<sup>+</sup>- dependent redox ribozymes were also evaluated.<ref>{{Cite journal |last1=Tsukiji |first1=Shinya |last2=Pattnaik |first2=Swetansu B |last3=Suga |first3=Hiroaki |date=2003-08-10 |title=An alcohol dehydrogenase ribozyme |url=http://dx.doi.org/10.1038/nsb964 |journal=Nature Structural & Molecular Biology |volume=10 |issue=9 |pages=713–717 |doi=10.1038/nsb964 |pmid=12910259 |s2cid=41081956 |issn=1545-9993}}</ref> The select ribozyme had a rate of enhancement of more than 10<sup>7</sup> fold and was proven to catalyze the reverse reaction - benzaldehyde reduction by NADH.<ref>{{Cite journal |last1=Tsukiji |first1=Shinya |last2=Pattnaik |first2=Swetansu B. |last3=Suga |first3=Hiroaki |date=2004-04-06 |title=Reduction of an Aldehyde by a NADH/Zn<sup>2+</sup>-Dependent Redox Active Ribozyme |url=http://dx.doi.org/10.1021/ja0495213 |journal=Journal of the American Chemical Society |volume=126 |issue=16 |pages=5044–5045 |doi=10.1021/ja0495213 |pmid=15099068 |issn=0002-7863}}</ref> Since the usage of adenosine as a cofactor is prevalent in current metabolism and is likely to have been common in the RNA world, these discoveries are essential for the evolution of metabolism in the RNA world.