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Last updated date: 17th Apr 2024
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What is Adenine?

Adenine Definition: Adenine is a purine nucleobase with an amine group at position 6 connected to the carbon. Adenine is the building block for nucleosides, adenosine and deoxyadenosine. The molecular formula for adenine is C5H5N5.

Adenine Meaning: Adenine (A) is one of four chemical bases found in DNA, along with cytosine (C), guanine (G), and thymine (T). Adenine bases on one strand forms chemical bonds with thymine bases on the opposite strand within the DNA molecule. The genetic instructions of the cell are encoded in a four-base DNA sequence. Adenosine triphosphate (ATP) is a type of adenine that serves as an energy-storage molecule and is used to power several chemical reactions inside the cell.

The chemical name of adenine according to the IUPAC is 9H-Purin-6-amine.

Structure of Adenine

The structure of adenine in isolated conditions is mainly the  9H-adenine tautomer. Several other adenine structures are also found that are mostly compounds that can be rapidly interconverted and are seen as equivalents.

2D Adenine Structure: 

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3D Adenine Structure(Conformer):

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Adenine only binds to thymine (and uracil in RNA) because it only has two hydrogen bonding sites, whereas cytosine only binds to guanine because it has three hydrogen bonding sites. Cells will store their blueprint for how a life form is formed using these four "code letters." From a design standpoint, the way these hydrogen bonds keep the nucleic acid strands together to form the double helix while still allowing them to "unzip" for replication and transcription is remarkable. This design is shared by all cells of all living organisms, no matter how basic or complex they are.

Properties of Adenine

C5H5N5is the chemical formula for adenine, a purine nucleobase. Purines are heterocyclic aromatic organic compounds that are heterocyclic in nature. Adenine is made up of two carbon rings: a pyrimidine ring and an imidazole ring, making it a purine. It is referred to as adenine residue when it is a component of DNA and is covalently connected to the deoxyribose sugar.     

             Molar mass:        135.13 g/mol

            Appearance:         White to light yellow, crystalline

                    Density:         1.6 g/ cm3(calculated)

         Melting point:         360 to 365 °C (680 to 689 °F; 633 to 638 K) decomposes

Solubility in water:        0.103 g/100 mL

                Solubility:        Negligible in ethanol, soluble in hot water and/or aqua 


           Acidity (pKa):         4.15 (secondary), 9.80 (primary)

Adenine Formation and Other Forms

The liver is where adenine is made in the human body. Since biological systems prefer to conserve energy, adenine is normally acquired via the diet, with the body breaking down nucleic acid chains to acquire individual bases and reassembling them via mitosis. Adenine synthesis requires vitamin folic acid.

When adenine is attached to ribose, it forms adenosine, a nucleoside, and when it is attached to deoxyribose, it forms deoxyadenosine, a nucleotide; when three phosphate groups are added to adenosine, it forms adenosine triphosphate (ATP), a nucleotide. One of the most basic methods of transferring chemical energy between reactions in cellular metabolism is adenosine triphosphate.

Biological Functions of Adenine

Guanine, cytosine, thymine, and uracil are the other four main (or canonical) nucleobases; adenine is one of them. The genetic code is made up of these basic nucleobases. The genetic code for a specific protein is contained in nucleic acids such as DNA and RNA molecules, which is dependent on the sequence of nucleobases. Nucleic acids play a crucial role in cellular functions, heredity, and organism survival.

Adenine is a crucial component of adenosine triphosphate (ATP), which is adenosine with three phosphate groups added to it, in addition to being the main component of nucleic acids. ATP is a high-energy molecule that is important for cellular metabolism and other biological processes.

The energy-rich adenosine triphosphate (ATP) and the cofactors nicotinamide adenine dinucleotide (NAD), flavin adenine dinucleotide (FAD), and Coenzyme A play a number of roles in biochemistry, including cellular respiration. It also serves as a chemical part of DNA and RNA and plays a role in protein synthesis.

Health Effects

The metabolic end product of purine metabolism, which includes adenine, is uric acid. Purines are abundant in the diet, especially in the liver, kidneys, and other internal organs. They can also be found in small quantities in beef, fish, cauliflower, beans, and mushrooms. 

Hyperuricemia is a disorder in which the body's uric acid level is too high. A high-purine diet can cause uric acid buildup, which can lead to gout (joint inflammation) and kidney stones. As a result, people with these conditions should eat a low-purine diet. It is also recommended that you avoid or limit your intake of alcohol and saturated fats because they obstruct purine metabolism.

Biological Reactions of Adenine

  • Purines are synthesised as ribonucleotides, not as free nucleobases, so adenine, like guanine, is derived from the nucleotide inosine monophosphate (IMP). The amino acids glycine, glutamine, and aspartic acid are used to make IMP, which is made from a pre-existing ribose phosphate. 

5-Phosphoribosyl-1-pyrophosphate(PRPP) is formed when ribose 5-phosphate interacts with ATP. PRRP is involved in purine and pyrimidine synthesis, as well as the formation and salvage pathways and NAD and NADP.

  • When the pyrophosphate of PRRP is substituted by the amide group of glutamine, PRRP is converted into a 5-phosphoribosyl amine, which is dedicated to purine biosynthesis. Purine biosynthesis takes place in the cytosol of the liver cell of humans. After that, IMP is converted into adenosine monophosphate (AMP) or guanosine monophosphate (GMP) (GMP). The energy source for the conversion of IMP to AMP is guanosine triphosphate (GTP).

  • Adenine Degradation: Adenosine » inosine (via the enzyme purine nucleoside phosphorylase) » hypoxanthine (via the enzyme xanthine oxidase) » xanthine (via the enzyme xanthine oxidase) » uric acid.

  • Exogenous purines including adenine and guanine are degraded in the liver of humans and other vertebrates. Uric acid is formed as a waste product as a result of purine degradation. The liver releases uric acid into the bloodstream, which then travels to the kidney. The substance is then excreted from the body by the urine. The catalytic activity of the enzyme adenine phosphoribosyltransferase can salvage and re-use adenine from catabolism.

FAQs on Adenine

1. Is Adenine a Vitamin?

Ans. Adenine was previously referred to as Vitamin B4 in older literature. Since it is synthesised by the body and is not needed for survival, it no longer qualifies as a vitamin and is no longer included in the Vitamin B complex.

2. Why is Adenine Toxic?

Ans. Adenine toxicity is caused by depletion of guanine nucleotide reservoirs, according to growth experiments with various purine salvage pathway mutants and the capacity of guanosine to avoid adenine toxicity. In wild-type cells, ATP pools increased twofold in the presence of adenine and stabilised after 5 minutes.

3. Mention the Difference Between Adenine and Adenosine?

Ans. Adenine is the precursor to adenosine, which is made by attaching a sugar moiety to a sugar moiety through a glycosidic bond. Adenine is a part of genetic material, while adenosine is a neurotransmitter and a precursor for adenosine triphosphate, which is the cell's primary energy source.