چكيده لاتين
The perspective of nucleic acids solely as genetic material in the forms of DNA and RNA changed in the early 1980s with the discovery of catalytic RNAs by Thomas Cech and Sidney Altman, and catalytic DNAs in 1994 by Breaker and Joyce. Nucleic acid enzymes can be classified into ribozymes, deoxyribozymes (or DNAzymes), and genetic polymers. Deoxyribozymes can be categorized based on the reactions they perform on nucleotide substrates, including DNA cleavage, RNA cleavage, RNA ligation, and DNA ligation.It is important to note that these enzymes require specific conditions such as particular environmental pH and specific concentrations of metal ions like Mn2+ for their catalytic structure. Both ribozymes and DNAzymes possess two different domains: one for enzymatic activity (the catalytic core) and another for substrate recognition (substrate-binding domains). Due to nucleotide similarity in the target sequence, there is sometimes a possibility that a DNAzyme might cleave a similar, non-specific substrate, known as the off-target issue. Specifically, a DNAzyme can recognize and cleave not only its designated specific sequence but also similar non-specific sites. Therefore, investigating and analyzing this issue is essential to improve, first, the effectiveness and then the efficiency of DNAzymes.To examine this issue, a DNAzyme named 6YR25, which adopts a catalytic structure in the presence of Mn2+ and Zn2+ cofactors, was selected. The substrate for this enzyme was chosen based on a part of the Hepatitis B virus genome, given the specific genomic characteristics of this virus that make it susceptible to single-stranded DNA cleavage by DNAzymes. Synthesized viral genomes in both non-mutated and point-mutated forms were used, and the DNAzymeʹs behavior in response to these substrates was analyzed under laboratory conditions. In each case, the Ymax and kobs of the reaction were calculated to assess the effect of substrate mutation on DNAzyme activity.
