Nucleic acid enzymes and complexes and methods for their use

A method for detecting the presence of a target nucleic acid in a sample, the method comprising

• (a) providing first and second oligonucleotide components and two nucleic acid substrates, wherein the first and second oligonucleotide components are capable of self-assembly in the presence of the target nucleic acid to form a catalytically active multi-component nucleic acid enzyme with a catalytic core having ligase activity (MNAzyme ligase) capable of ligating the two nucleic acid substrates, wherein the first and second oligonucleotide components are first and second partzymes respectively, and each of the first and second partzymes comprises a catalytic core portion, a substrate arm portion, and a sensor arm portion, and the catalytic core portion is between the substrate arm portion and the sensor arm portion;
• wherein the sensor arm of the first partzyme and the sensor arm of the second partzyme can hybridize adjacent to each other on the target nucleic acid and the substrate arm portion of the first partzyme and the substrate arm portion of the second partzyme can hybridize to the two nucleic acid substrates so that the two nucleic acid substrates are adjacent each other on said catalytically active MNAzyme ligase and thereby capable of ligating each other on said catalytically active MNAzyme ligase and the substrate arm portion of the first partzyme and the substrate arm portion of the second partzyme are adjacent each other on said catalytically active MNAzyme ligase when the target nucleic acid is present in the sample,
• (b) contacting the first and second oligonucleotide components and the two nucleic acid substrates with the sample under conditions permitting self-assembly of the catalytically active MNAzyme ligase when the target nucleic acid is present in the sample, and
• (c) determining the ligase activity of the catalytically active MNAzyme ligase by detecting a ligated nucleic acid product formed by ligation of a 5′ end of one substrate of the two nucleic acid substrates to a 3′ end of other substrate of the two nucleic acid substrates, wherein the presence of the ligase activity of said catalytically active MNAzyme ligase is indicative of the presence of the target nucleic acid in the sample.