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Ribonuclease is a type of nuclease that catalyzes the degradation of RNA into smaller components. Ribonucleases can be divided into endoribonucleases and exoribonucleases, and comprise several sub-classes within the EC 2.7 and 3.1 classes of enzymes.
Ribonuclease H is a family of non-sequence-specific endonuclease enzymes that catalyze the cleavage of RNA in an RNA/DNA substrate via a hydrolytic mechanism. Members of the RNase H family can be found in nearly all organisms, from bacteria to archaea to eukaryotes.
Exodeoxyribonuclease V is an enzyme of E. coli that initiates recombinational repair from potentially lethal double strand breaks in DNA which may result from ionizing radiation, replication errors, endonucleases, oxidative damage, and a host of other factors. The RecBCD enzyme is both a helicase that unwinds, or separates the strands of DNA, and a nuclease that makes single-stranded nicks in DNA. It catalyses exonucleolytic cleavage in either 5′- to 3′- or 3′- to 5′-direction to yield 5′-phosphooligonucleotides.
In molecular biology, endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain. Some, such as deoxyribonuclease I, cut DNA relatively nonspecifically, while many, typically called restriction endonucleases or restriction enzymes, cleave only at very specific nucleotide sequences. Endonucleases differ from exonucleases, which cleave the ends of recognition sequences instead of the middle (endo) portion. Some enzymes known as "exo-endonucleases", however, are not limited to either nuclease function, displaying qualities that are both endo- and exo-like. Evidence suggests that endonuclease activity experiences a lag compared to exonuclease activity.
Exonucleases are enzymes that work by cleaving nucleotides one at a time from the end (exo) of a polynucleotide chain. A hydrolyzing reaction that breaks phosphodiester bonds at either the 3′ or the 5′ end occurs. Its close relative is the endonuclease, which cleaves phosphodiester bonds in the middle (endo) of a polynucleotide chain. Eukaryotes and prokaryotes have three types of exonucleases involved in the normal turnover of mRNA: 5′ to 3′ exonuclease (Xrn1), which is a dependent decapping protein; 3′ to 5′ exonuclease, an independent protein; and poly(A)-specific 3′ to 5′ exonuclease.
Ribonuclease III (RNase III or RNase C)(BRENDA 3.1.26.3) is a type of ribonuclease that recognizes dsRNA and cleaves it at specific targeted locations to transform them into mature RNAs. These enzymes are a group of endoribonucleases that are characterized by their ribonuclease domain, which is labelled the RNase III domain. They are ubiquitous compounds in the cell and play a major role in pathways such as RNA precursor synthesis, RNA Silencing, and the pnp autoregulatory mechanism.
UvrABC endonuclease is a multienzyme complex in bacteria involved in DNA repair by nucleotide excision repair, and it is, therefore, sometimes called an excinuclease. This UvrABC repair process, sometimes called the short-patch process, involves the removal of twelve nucleotides where a genetic mutation has occurred followed by a DNA polymerase, replacing these aberrant nucleotides with the correct nucleotides and completing the DNA repair. The subunits for this enzyme are encoded in the uvrA, uvrB, and uvrC genes. This enzyme complex is able to repair many different types of damage, including cyclobutyl dimer formation.
Drosha is a Class 2 ribonuclease III enzyme that in humans is encoded by the DROSHA gene. It is the primary nuclease that executes the initiation step of miRNA processing in the nucleus. It works closely with DGCR8 and in correlation with Dicer. It has been found significant in clinical knowledge for cancer prognosis and HIV-1 replication.
Exoribonuclease II is an enzyme. This enzyme catalyses the following chemical reaction
Deoxyribonuclease IV (phage-T4-induced) is catalyzes the degradation nucleotides in DsDNA by attacking the 5'-terminal end.
The degradosome is a multiprotein complex present in most bacteria that is involved in the processing of ribosomal RNA and the degradation of messenger RNA and is regulated by Non-coding RNA. It contains the proteins RNA helicase B, RNase E and Polynucleotide phosphorylase.
Restriction endonuclease (REase) EcoRII is an enzyme of restriction modification system (RM) naturally found in Escherichia coli, a Gram-negative bacteria. Its molecular mass is 45.2 kDa, being composed of 402 amino acids.
The enzyme exodeoxyribonuclease VII is a bacterial exonuclease enzyme. It is composed of two nonidentical subunits; one large subunit and 4 small ones. that catalyses exonucleolytic cleavage in either 5′- to 3′- or 3′- to 5′-direction to yield nucleoside 5′-phosphates. The large subunit also contains an N-terminal OB-fold domain that binds to nucleic acids.
Ribonuclease T2 is an enzyme. It is a type of endoribonuclease. This enzyme catalyses the following chemical reaction
Exodeoxyribonuclease III is an enzyme that catalyses the following reaction
Ribonuclease IV is an enzyme. This enzyme catalyses the following chemical reaction
Ribonuclease is an enzyme. This enzyme catalyses the following chemical reaction
Ribonuclease E is a bacterial ribonuclease that participates in the processing of ribosomal RNA and the chemical degradation of bulk cellular RNA.
The retroviral ribonuclease H is a catalytic domain of the retroviral reverse transcriptase (RT) enzyme. The RT enzyme is used to generate complementary DNA (cDNA) from the retroviral RNA genome. This process is called reverse transcription. To complete this complex process, the retroviral RT enzymes need to adopt a multifunctional nature. They therefore possess 3 of the following biochemical activities: RNA-dependent DNA polymerase, ribonuclease H, and DNA-dependent DNA polymerase activities. Like all RNase H enzymes, the retroviral RNase H domain cleaves DNA/RNA duplexes and will not degrade DNA or unhybridized RNA.
Ribonuclease U2 is an enzyme. This enzyme catalyses the following chemical reaction
References
- ↑ Gurevitz M, Watson N, Apirion D (June 1982). "A cleavage site of ribonuclease F. A putative processing endoribonuclease from Escherichia coli". European Journal of Biochemistry. 124 (3): 553–9. doi:10.1111/j.1432-1033.1982.tb06629.x. PMID 6179777.
- ↑ Watson N, Apirion D (November 1981). "Ribonuclease F, a putative processing endoribonuclease from Escherichia coli". Biochemical and Biophysical Research Communications. 103 (2): 543–51. doi:10.1016/0006-291X(81)90486-1. PMID 6277308.
