Aptamers, aptazymes, DNAzymes
Fig. 1: The three classes of functional nucleic acids (A) DNAzyme, (B) aptamer (C)aptazyme.
Traditionally, nucleic acids are thought of as data storage molecules.They store and transfer genetic information for protein expression. Proteins can perform many chemical functions, such as catalysis (protein enzymes) and binding of target molecules (antibodies). It turns out that such functions can also be performed by nuclei acids. These effects were not explored unitl the 1980s, when the first catalytic RNA molecule was discovered. Following that, many more catalytic RNA were found both in nature and isolated in the laboratory with combinatorial in vitro selection. In 1994, this method was applied to obtain catalytic DNA.
Thanks to these advances, three classes of functional nucleic acids have been developed. Fig. 1 gives a summary on each class of the nuclei acids and their relations to each other. DNAzymes are DNA molecules with catalytic activities (catalytic RNA are known as ribozymes). For the cleavage-bsed DNAzymes, the enzyme strand cleaves the substrate strand into two pieces (Fig. 1A). Aptamers are nucleic acid molecules with specific binding functionality. In the presence of targets, aptamers adopt complementary 3D conformation which can preferentially bind the targets (Fig. 1B). Rational combination of DNAzymes and aptamers can result in aptazymes (Fig. 1C), which may have the property of binding triggered cleavage.