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It is one of the four main bases in deoxyribonucleic acid, ribonucleic acid, adenine, guanine, and thymine.
It is a pyrimidine derivative with a heterocyclic aromatic ring and two substituents attached (an amino group in the 4-position and a keto group in the 2-position). The nucleoside of the cytosine is cytidine. In the Watson-Crick base pairing, it forms three hydrogen bonds with guanine.
Cytosine is one of the five main nucleobases that store and transport genetic information within a cell in the nucleic acids DNA and RNA. The other four nucleobases are adenine, guanine, thymine, and uracil.
Cytosine, thymine, and uracil are derivatives of pyrimidine, while guanine and adenine are purine derivatives. The nucleoside of the cytosine is cytidine.
In DNA, cytosine (C) and thymine (T) form hydrogen bonds with their complementary purine derivatives, guanine (G) and adenine (A). In RNA, the complement of adenine is uracil (U) instead of thymine.
Therefore, cytosine, adenine, and guanine are present in DNA and RNA, while thymine is generally observed only in DNA and RNA.
In the mating of Watson-Crick bases, the cytosine forms three hydrogen bonds with guanine. From the point of view of the structure, it is notable that cytosine, with its three binding sites, only adheres to guanine in DNA. In contrast, with two areas for hydrogen bonding, adenine only adheres to the thymine.
How these hydrogen bonds hold the strands of the nucleic acid together to form the double helix, and at the same time, allow the strands to “decompress” for replication and transcription, is simply fantastic from the design point of view.
Cytosine can also be part of a nucleotide unrelated to DNA or RNA.
Like cytidine triphosphate (CTP), it can act as a cofactor for enzymes and can transfer a phosphate to convert adenosine diphosphate (ADP) to adenosine triphosphate (ATP). ).
History of cytosine
Cytosine was discovered and named by Albrecht Kossel and Albert Neumann in 1894 when it was hydrolyzed/isolated from the tissues of the calf thymus. A structure was proposed in 1903 and was synthesized (and thus confirmed) in the laboratory in the same year.
Cytosine recently found use in quantum computing.
The first time the properties of quantum mechanics were used to process information occurred on August 1, 1997; cytosine was used in an early demonstration of quantum information processing when researchers from the University of Oxford implemented David Deutsch’s algorithm. Jozsa
It was implemented in a two-cubic NMRQC (Quantum Nuclear Magnetic Resonance Computer) of two qubits based on the cytosine molecule.
In March 2015, NASA scientists reported cytosine formation, along with uracil and thymine, from pyrimidine under laboratory conditions similar to space conditions. It is interesting because pyrimidine has been found in meteorites, although its origin is unknown.
Chemical reactions
Cytosine can be found as part of DNA, as part of RNA, or as part of a nucleotide.
Like cytidine triphosphate (CTP), it can act as a cofactor for enzymes and can transfer a phosphate to convert adenosine diphosphate (ADD) to adenosine triphosphate (ADT). ).
In DNA and RNA, cytosine is combined with guanine. However, it is unstable and can be transformed into uracil (spontaneous deamination). This can lead to a point mutation if DNA repair enzymes do not repair it, such as uracil glycosylase, which cleaves uracil in DNA.
When it is in third place in an RNA codon, cytosine is synonymous with uracil since they are interchangeable as the third base. The third is always interchangeable when found as the second base in a codon. For example, UCU, UCC, UCA, and UGC are all serines, regardless of the third base.
The cytosine can also be methylated in 5-methylcytosine by an enzyme called DNA methyltransferase or be methylated and hydroxylated to form 5-hydroxymethylcytosine.
Active enzymatic deamination of cytosine or 5-methylcytosine by the APOBEC family (apolipoprotein B mRNA editing enzyme, similar to catalytic polypeptide) of cytosine deaminases could have beneficial and detrimental implications in various cellular processes, as well as in the evolution of the organism.
The implications of deamination on 5-hydroxymethylcytosine, on the other hand, remain less understood.
Theoretical aspects of cytosine
Cytosine has not been found in meteorites, suggesting that the first strands of RNA and DNA had to look elsewhere to obtain this essential element.
The cytosine probably formed within some parent bodies of meteorites. However, it did not persist within these bodies due to an effective deamination reaction in uracil.
Properties
Cytosine is a pyrimidine derivative with a heterocyclic aromatic ring and two substituents attached (an amino group at position four and a keto group at position two).
Heterocyclic compounds are organic compounds (those containing carbon) that contain a ring structure that includes atoms in addition to carbon, such as sulfur, oxygen, or nitrogen, as part of the ring.
Aromaticity is a chemical property in which a conjugated ring of unsaturated bonds, lone pairs, or empty orbitals exhibits a more muscular stabilization than expected with the stabilization of the conjugation alone.
In organic chemistry, a substituent is a substituted atom or group of bits instead of a hydrogen atom in the original chain of a hydrocarbon.
In DNA and RNA, cytosine is combined with guanine. However, it is unstable and can be transformed into uracil (spontaneous deamination). This can lead to a point mutation if it is not repaired by DNA repair enzymes, such as uracil glycosylase, which cleaves uracil in DNA.
